IlDEJBrJDEUROPEAN INCOHERENT SCATTER SCIENTIFIC

ASSOCIATION

ANNUALREPORT19S9

S-981 28 KIRUNA, S'WEDEN

Vl-lr 5YSrE:.M

The EISCAT Radar Systellls

(see page 2 for a more deIQiled descriptioll)

The cover illustration is a colour representation of the meridional wind velocities in the altituderange 55 to 80 km measured by the EISCAT UHF radar operating the Unusual Programme,UP-l. The data depicted spall the time illterval1300 to 1530 UT 01123 Detober 1989. ThesemeasuremenlS were made possible by the precipiratian of energetic protons deep inta theatmosphere during a solar proton event (SPE) where they caused both D-region ionization andthe resulting polar cap absorption (PCA) of radio signals. Such events occur preferentialfy nearsunspot maximwn, as was the case in 1989 when several similar data sets were obtained. Theenhanced echoes from the D-region during SPE's support important studies of neutralarmosphere dynamics in this region, which is normalfy inaccessible by radar. The colour scaleruns from red, represeming winds blowing southward at 50 m s·}, through green, correspondingto zero morian, to blue, wlzich represents northward winds of50 m s'}.

ANNUALREPORT1989

EISCAT, rhe Europeanlncoherefll Scarrer Scienrijic Association, is esrablished roconducr research on rhf! miMle and upper armosphere, ionosphere and aurorausitlg rhe itlcoherenr scaUer radar recJmique. This technique is rhe mosr powerfulground-based roolfor rhese research applications. EISCAT is also being used as acoherent scarter radar for swdying insrabilities in rhe ionosphere as weil as forinvestigating the structure and dynamics of the middle atmosphere and as adiagnostic instrwnent in ionospheric modijication experiments (Heating).

There are seven incoherent scaller radars in the world, und EISCAT operates I'lVOof the highest-srandardfacililies. The experimental sites of EJSCAT are located inScandinavia, nonh of the arctic circle. They consist oj two independent radarsystems (see schematic on the inside of the front cover).

The EISCAT UHF radar operates in the 931 MHz band with a peak tronsmillerpower of 15 MW and 32 m, fIllly steerable parabolk dish antennas. Thetransmiuer and one receiver are in Trams", (Norway). Receiving sites are alsolocated near Kiruna (Sweden) and Sodankylä (Finland), allowing cnntinuoustristatic measurements to be made.

The mOfwstalic VHF radar in Troms~ o{}erares in the 224 MHz band with a peaktransmitter power of 15 MW (lo be raised to 4 MW) and el 120 m x 46 m paraboliccylinder anrenna, which is subdivided into four secrors. Ir cafl be steeredmechanically in the meridional plane from 30·south to 60· north of the zenitll.

The basie dara measured with the incohereflt scaller radar technique are profilesof electron density, electron and ion temperature and ion velocity. Subsequenrprocessiflg also allows a wealth offurther parameters, describing the iOflosphere,upper atmosphere and mesosphere, ro be derivedfrom these. A selection of weil­designed radar pulse schemes allows the adaptation of the data-taking routjnes romany partieular phenomena. occurring at altjlUdes between about 60 km and morethan 1000 km. Depending on geophysical condiriollS, a best time resolUlion ofberrer than one second and an altjtude resolution of a jew hundred meters can beachieved, whereas rypical resolutions are of the order of minutes and kilometres.

Each year, 2000 operating hours (nominal) are distributed equally bel'lVeenCommon Programmes (CP) and Special Programmes (SP). At presefIl six well­dejined Common Programmes are rUtI regularly for 24 hours, or more, abom30 times per year lO provjde a data base for long term ~ynoptie sllldies. ThreeUnusual Programmes (UP) are started ad hoe during particular geophysicalconditiofls. A large nwnber of Special Programmes, defined individua/ly byassociate scientists, are run to study a variety ojspecijic geophysical evems.

The Annual Reporrs prf!sent a summary of EISCAT's operations, developmems,scientijic resulrs, publications and budget for eac;h year. Further derails of theEISCAT system and operation can befound in various EISCAT repons, includillgan illustrated brochure, which can be obrained from EISCAT Headquarters inKiruna, Sl·veden.

The jnvestmenu and operationai cOSts of EISCAT are slwreJ betH;l'Cfl:

SIwmen Akatemia, FinlandCenfte National de la Rec:herche Scielllifiqlle. France

Max·Planck·Gesellschajt, Federal Republic ofGerman,\'Norges Almenvitenskapelige Forskningsråd, Nonvay

Naturvetenskapliga Forskningsrådet, SweJl'nScil:nce and Engineering Resea/'ch Council, United Kiflgdonl

EISCAT ANNUAL REPORT 1989CONTENTS

Council Chainnan's ForwardDireclor's IntroductianOperations

The Year in PieturesCatalogue of Observations

Scientific Research and DevelopmentsMesosphere and D-regionE-Region StudiesF~Region StudiesAuroral InvestigationsHigh-Iatitude Convection/Magnetospheric ResponsesNon-thennal PlasmasOther Scattering PhenomenaIonospheric Modification (Hearing)Digital Signal Processing

Appendices

Publications1989 JournalsOther Publications

EISCAT Repans and MeelingsBudge, Balance Shee' 1989EISCAT Council, Commiuees and Senior StaffThe EISCAT AssociatesAddresses

Annual Report 1989 of the EISCAT Scienlific Association

Editing and lay·out by:Tony van Eyken and Jiirgen Röttger,EISCAT Headquarters, Kiruna, Sweden

Finishing and Printing by:Birgiua Määuä and Stig Björklund,Institulet för Rymdfysik, Kiruna, Sweden

1SSN 0349-2710

page

45

1112

131621212928373941

434648495051

Back Cover

4

COUNCIL CHAIRMAN'S PAGE

This year has been a very successful one for EJSCAT. Many oUlstandingproblems have been resolved, new initiatives staned and, above all. excellentscience has been produced. Demand for ElSCAT time remains high andonce again the system has been operated for slightly longer than the nominal2000 hours in order to satisfy user requesls. New Common Programmeshave been intnxluced and il is particularly gratifying to nOlc that the VHFCommon Programmes are now operational.

Major progress has been made with the elimination of the problems ofintcrference caused by the Nordic radio tclephone system. However, samedifficulties still remain with regard 10 VHF interferenee at Troms~. All thoseinvolved are to be congratulated for their efforts to reach mutually acceptablesolutions to these difficulties. Some VHF klystron problems are still with us,although satisfaclory operation of the VHF transmitter has been possibleduring the year.

A major extension of ElSCAT activities will result from the take-over of theMax-Planck-Institut fUr Aeronomie Heating facility at Troms~. This will adda new dimension to the kind of science that ElSCAT can undertake and weare greatly indebted to the Max-Planck-GeseUschaft and the resean:hcouncils of the Associate countries for providing the financial support for thisimportant development. Following an invitation from one of the Associatecountries, ElSCAT is planning to become involved in a new Polar Caplncoherent Scatter Radar (peR) to be located on Spitzbergen. lt is envisagedthat this new radar will form an extension of the EISCAT facilities to thepolar cap regions. Collaboration in this project is being actively encouragedwith a view to fonning a group to produce a system design for the PCR.

There have been a number of staff changes during the year. I would like tothank those who have left, for their contributions to EISCAT, and welcomethose who have joined during the year. My particular thanks go to theDirector and his staff for their help and guidance during my fLrst year asChainnan.

T/ulor Jones

DlRECTOR'S INTRODUCTION

The year 1989 was one of good progress though a few misfol1unes appeared and cantinue toharnper the full VHF operation. On the average, however, the UHF system is in a very heallhyshape and the VHF system undergoes a systematic upward trend. which is demonstratcd forinstance by the new science resulting from many VHF experiments. I am pleased to repan aboutthe major events. highlighls and developmcms of EISCAT in this introduction to me AnnualRepen 1989.

Several Special Programme campaigns look place and the Common Programme operationcontinued as usual. Previously, Common Programmes used only the UHF system, but now VHFCorrunon Programmes have also been successfully lested, for example the D-region/mesosphereprogranmlc CP-6 and the high~altilude programme CP-? Overall, VHF Common Programmeoperations amounted to 79 hours, equivalent to 7% of the total Common Programme time of1115 hOUTS. Also the new UHF COIIUllon Programmes CP-4. (high-Iatitude programme) andCP-5 (optimised for lower thennosphere studies), were run for extended periods of about 100hOUTS each to serve the purposes of World Day campaigns for GlSMOS (Global IonosphericSimultaneous MeasuremenlS of Substorms) and LTCS (Lower Thermosphere Coupling Study).Close to 100% of the Common Progranune data have been analyzed, which is a good sign of thehigh reliability of (he system. It is now also possible to routinely obtain the full vector velocitiesduring Common Progranunes by combining the data from all sites in real-lime. Several UnusualProgrammes operations took place, mostly to take data with the low-altitude UHF programmeUP-l during same of the strong solar proton events which occurred during 1989. The front coverof this Annual Repon shows the meridional velocities in the mesosphere revealed by enhancedelectron density during such a solar proton event. At times the UHF radar and the VHF radarwere also operated simultaneously.

Special Programmes were conducted over 1157 haurs. Together with the Common Programmeoperation this adds up to a total of 2272 hours of EISCAT experiment operation during the year1989. This is again higher than the target of 2000 hours and inclicates bOlh the strong demand forexperiment time by Associate scientists and participation in longer World Day operations as weilas the high reliability of the system. The percentage of Special Programme operations perAssociate in the year 1989 (the values in brackets give the accumulated usage) were:

FranceUnited KingdomGennanySwedenNorwayE1SCATFinland

37%25%17%8%7%5%1%

(25%)(28%)(21%)( 9%)( 9%)( 5%)( 3%)

More (han ISO haurs (13%) of (he Special Programme operalion were with the VHF system,although this is still limited tO 1.5 MW peak power, and beam directions between north andvertical only. A breakdown of operations in 1989 can be found on pages 11 and 12.

The total nurnber of dala tapes handled by E1SCAT in the year 1989 arnounts to almost 1700, ofwhich 90 were analysed Conunon Programnle dala. These are regularly distributed to the datarepresentatives of the Associates and those for the World Day operations are also sent lO theIncohcrent Seatter Radar Data Base at NCAR in Boulder.

The Headquaners c:olllputer was upgraded by providillg access 10 a new Norsk Data ND 5400,which is shared between EISCAT and the Swedish Institute of Space Physics (lRF) in Kiruna.The genent.1 evolution of thl:: computing systems at the EISCAT sites and Headquarters is directed(owards a graduaJ challge to local area networks of workstations and induslrial-standard PCs. Ilis anticipated that Ihese arrangemenlS will al10w flexible and reliable operations, enriched.dataanalyses by EISCAT staff and visitors and wi~l. l:nake EIS~AT mC!re independent of sl~glecomputer suppliers. In the context of data acq111SlIlOn evolution, the IOtegrator-decoder proJect

5

(MUFFlN) to allow on-line decoding of the newly applied alternating and complementary codes,has made funher progress at the Sodankylä site. Another project, shared with the IRF, is thedesign of a new digital spc::ctrum a.nalyzer (FFT Processor), which will allow high speed on-linespectrum analys is. The rnemories of the present radar controllers are being extended from4 kWords to 32 kWords, which allows the application of mOTe sophisticated eodes. It is now alsopossible to preload codes into the buffer memory, which pennits some alternating pulse schemesto be decoded on-line using an additional hardware decoder installed in the correlator asdescribed on page 41 of this repan.

Substantial improvernems have been achieved in eliminating the effeets of the NMT 900 mobiletelephone transmitters on our recdving systems in Kiruna and Sodankylä. This became possiblethrough the insertion of spedal bandpass filters and high power mixers; the local oscillators havealso been exchanged and modified 10 rc::duee noise sidebands. It is, for instance, again possible toperfonn observations with such extreme requirements as those of radio astronomy. The Troms~

receiver from end has also been irnproved to optimize the transmiHeceive transition effeets andfurther reduce the noise figure. The UHF transmitter cominues 10 be one of the most reliableparts of the system and it is operated eontinuously for roany days during extended World Day andSpecial Programme eampaigns at power leve!s of 1.5 MW and full duty eyele.

In the course of mutine system maintenance, inspections of the VHF and UHF antennas weremade by outside experts in spring 1989. The antennas were found to be in generally good shapeand, in addition, we are now proceeding with further improved preventive maintenance andinspection procedures. Particularly the summer months are being used for this purpose, such aswork on pimle bearings, oi! exchange, sealing of bearings, mil and basement inspections andrepair and paillting of steel members and surface elements of the VHF antenna. Specialarrangements have been worked out for safe-guarding the antenna in Sodankylä when the walerlevet of the nGarby Kitinen river will be raised in a few years.

The VHF transmitter was still operated with only one klystron at 1.5 MW and redueed duty cycleof 7.5%. In the beginning of the year 1989 we experienced a break of the filament of klystronYK1320/2, and this klystron was retumed for repair to the factory in Hamburg. After inspectionit was decided to redesign the filament construction and to exchange the heater transfonners.Because of leaks in the klysn'on output coupling, which occurred during the factory processing,the replacemel1t of certain material parts were also considered. This has delayed the replacementof this klystron YK1320/2 into the year 1990.

The rebuilt klysn-on YK1320/1, which had been instalied in Troms~ in autumn 1988, was usedsuccessfully in experiments. It was not possible to accept this klystron at that time. but EISCATwas penniued 10 ron it with reduced operating parameters. A break of a eooling pipe andflooding of pan of the transmiuer happened in July. This did not affect the perfonnance of thek.1ystron but destroyed some of the magnet eoils. Further adjustments and tests of the klystronfollowed, during which a vacuum leak occurred, which was fixed by the Philips engineers on sitein Troms~. The acceplance (est perfonned in October 1989 showed output power of the order of2 MW, which is less than the specificatiolls. The resulting negotiations on payment reductionscontinue into the year 1990.

Because of all lhe uncertainties experienced. we decided 10 prepare a feasibility study for analternative VHF transmiuer, whieh could be used in case bOlh klystrons evenlually fai!. 5uch aVHF transmitter could use gridded tubes, instead of klystrons, and would further al10w anelectronic east-west antenna beam steering.

The intelferenee, which is still caused in the immediate neighbourhood by the VHF operation,results from spill-over from the antenna refleelor surface when the antenna beam is paintingsouth of the zenith. We have investigated several possibilities 10 mitigate these spill-over effeets.such as fencing the antenna, extending the renector surface or changing the feed systemmechanically or electrically, in addition to electronic hardening and shielding of affectedequipment. Only the latter rneasures appear to be feasi~le and we have ma~e ~ood .pro~ress inthis work. It can now be noted that the VHF system mterference and radiation sltuatlon has

6

irnproved and EISCAT in its present configuration, with vertical and northward beam directions,is certainly operating weIl below official hazard limits. Since new equipment may be broughtinto the neighbourhood, and could be affecttd by the EISCAT operation, we have to continue theelaborate work on interference mitigation by improving the shielding and screening of equipmentand houses in order to eliminate any further complaints. This work is particularly important forthe planned VHF i:lJ1,tenna contigW'ation which should allow the automatic electronic west-eaststeerability of the antenna beam.

Following long procedures and llegoli<.ltloils with the telecommunication administrations ofNorway, Sweden und f~J)!atld, thl- pcolOng;lllon of the operating permit for the EISCAT Trorns~

transmitters was issued at rhc end n1' the year 1989. In principal, this pennission is valid until1998, but it need~ to be r~(ull~!olcrcd e'/~IY two years in order to take inta account changingoperating conditi\JILs Uj\\! trC:t.!L1elli,;Y UJlO\;i1UOIlS to other radio systems in or close to the EISCATband~. The issuc of thc 0Pl~HIH!lg pennit is recognised with great appreciatian to thetelecommunicalion adminislratiom; i'llld il is expected that the operating conditions imposed onEISCAT are acceptablo.

Many visiting sciclItists spcnt ulne in Kiruna, Troms~ and Sodankylä to perfonn experimentswith the EISCAT radars and aJso brought their own instrumentation, such as optical devices anddigital instruments. Thc:: visitors and operators can now use aredesigned controi room in Troms~

which separates the conU'ol and monitor terminal devices from the radar contral, monitor andacquisition instrUl11enrs. MallY visitors from the general public enjoyed tours of the EISCATsites and EISCAT particIpated also at the:: Technical Exhibition in Stockholm in autumn 1989.For this purpose a specialleaflet, describing the EISCAT Scientific Association, ilS structure andoperation, the scientific goals and the scic:ntitic fesults, was prepared. This leaflet is reproducedin Table 1. We have also prep~d a special computer slide show for a tutorial introduction to theineaherent scatter technique using EISCAT. Thc:: Freneh Associate has made available a copy ofthe video movie 'Nuit d'Aurores: les relations soleit-terre', of which an English translation wasprepared for distribution to all Associates. In August we appreciated the visit of the Chainnan ofthe Astronomy and Planetary Science Board of the Science and Engineering Research Council ofthe United Kingdom, Professor Arnold Wolfendale, and 'he Secretary of the EISCAT CouncilChairman, Ian Midson, to the Trornsgs site. The Director and other Slaff members showed himthe si,e and ilS opera'ion, see Fig. 1. In November the EISCAT Council Chairman, ProfessorTudor B. Jones, paid a visit to the Trams" site.

F/g. I. In AugusI 1989 Professor ArnoldWolfctldale, CJrairman of the SERCA:Utonomy and Planetary Science Board,togetJler with the Secretary of the EISCATCouncil Chairman, lan Midson, visited theEISCA1'Trom.s~ site. The photo shows (fromfront tu back) Professor A. Woljendale,Dr. J. Röuger, Dr. A.P. van Eyken andMr. I. Midson next to the end of the VHFQntennafeeder bridge.

7

EUROP8AN INCOHERENT SCATIER SCIENTIFICASSOCIATION

S-981 28 KIRUNA. SWEDEN

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Table l: The EISCAT LeafIet

8

I~COHtRO<l SCATn:M MAUAM MI::.~""'RLIl

m' TUt I'Q..... IUSOnltEME 'MI LPPER A1"1tIS~IlERt:

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"I' '. '---- <---- _-.k;. ...,...,...__..._ _-j ./·1 /~.,;,I@

) .

n........10.. ....-..... '" " ...-.,br" ~k~ '"'_ lO ~ """-'" ..,.j -- , -~.. ••~ , JI"'"' ...~n.... "" '1> om .."" "" pII< """' < ""'......._ '''''''''''"1 .11«b '" .....r""" ....._ •..,...•• 1M ,,'""1""1""" <>I ...... ......"Il ........... ,w <lir "" ""' u. ,,","""' , "f'Io<"'-" ""... ,"",,,",,"'-II <'><.F' '" ,'"-....... --..J",~

lO '''' bo<l.,..-l _""""........ .......,t..I, "",.,....__ ....,"" 1..14. _ .. """"ly , ....>111<T1oo>< , .....,_~ ~ _o.dI) ~I

ISR ...."""""".,.... I I ....__....... pII<_~ I' .

_'" P""l ."' _ ~ .._....... , "'""""' _..'"_.

lUda,_ al .... _ .ff........ {oIIl>lO , ' y•. ,_ at , b <lo< v.-... ,._"' "__ r'''''' p"<".._ _''''' ......-.. "" ""'_ - "'" " .",..,.,...,. '""h ,,'''-,,0<, <.. O: ..,<~, , "'" '"''''''' , Il'RI",_", ,'.._ ''''"'''''n '' ,,'" .uh ""_ .. ",< 1" .,."...,•. _I ., ,h. '" ."- "'" 1"-'., ...__ ond _' ,..,"''' 1"''';00' , v..~ , "., .. ""I"'""'''''''>tid "~.lt,,, ,"'.0" ""J ...,..,. ' h ' "l "" ..r••Th< l'l.."" I'o>w .. "" pII<....""",,, "lO. " ,,"' ' " ..""",r,,,,,... ot ""' pII<'" <011'«'- lIIJ ,,.. , ,"'.., 01 ,,.. """" .,' ,;'""'P'_'"" ""'..'''' ro" ...tIo .... E.l lfI< " ~I< ",..., .."" ISM..."••_ 01 """"""'" pM<I<'''' lo bock lO "" .....oph<.. o"Il ""'<0:0"'- l«v«I, ... P""'''' "'" I'.onh·.U"lfI<'''- flo" ''''''' ho:~ "" ..<d<f ,o. ,"""'''''..,... , __., 01 .......""..."""", ."'_ 110101 _ ... polot ~< '" , "' ' """'*........ 11«.."'01 _ at .....1«.... "'."'1 " '_ _ .......... """""""... _ ",~_" , .. lit _ ,1 l>! '..-..,.. '""'I<t , "" -nooI') b'" ""' ' U ••• <dl -.. """"'Il' at • fr.. 'lo L' " " ,m ., ".-. I~ .,"- 1110 .....- '" .. EN.H _ "" ,.o1<t ..~ s.........,.. _ odl uI ...... <1""" ...... "" _ 1 ,,, .. ~ _ .............. .ud polO ot *" pabt Uf

Table l (cont"d): The EISCAT Leaflet

[ntemal Executive and Budget Meetings take place twice per year. [n these meetings theDirector, his Deputy, the Business Manager, the Head of Computer Operations. the SeniorScientist and the Site Leaders discuss and agree upon operational, administrative, personnel andbudgetary maners. The spring meeting was at Headquaners and the autumn meeting in Troms0.The E[SCAT AmlUal Review Meetings usually take place in March. The 1989 meeting was heldat Hetta/Enontekiö in notthem Finland ~d was organised by the Sodankylä site staff. The springAdministrative and Finance Conuninee meeting was held in Hamburg and the spring ScientificAdvisory Committee meeting was held before the Founh EISCAT [nternational Workshop inJune in Sigtuna near Stockholm. At the end of September the AFC met at the Troms0 site andthe SAC met in October in Kiruna. ElSCAT International Workshops are held about every twoyears and bring together the scientists working with EISCAT to present and discuss their results.The 1989 workshop was organised very effectively by the Uppsala Division of the [nstitutet förRymdfysik (lRF, SwOOish Institute of Space Physics). About eighty paniciparlts attended andlistened to almost 70 scientific presentations. On behalf of the host Associate the Councilrnember Professor Bengt Hultqvist made the opening remarks and the EISCAT Directorpresenled an introductory note 011 'EISCAT: Progress-Malurily-Evolution'. The workshopparticipauts were honoured by the appearance of the General Secretary of the NaturvetenskapligaForskningsrådet (NFR) of Sweden. Professor Carl NordJing, as weil as several members of theElSCAT Council, SAC and AFC.

[n November, the E[SCAT Council met at the Rutherford Appleton Laboratory in the UnitedKingdom and was honoured by the participation at dinner of several representatives of theRutherford Appleton Laboratory and the Science and Engineering Research Coun~il. D~~g thisCouncil meeting, il was decided thal EISCAT should take over the Heating Faclhty. atRarnfjordmoen, which has been constructed and is presently operated by the Max·Planck-lnStllutfUr Aeronomie. The scienlific expeclations of the Beating research are inc1uded in a special

9

repon, which was prepared by an active group of scientists using ElSCAT and the Heatingfacility. From the year 1993, E1SCAT will own and operate this facililY which will allow morecombined EISCAT operations during ionospheric modification experiments. Resulting from aproposaI by the United IGngdom, plans are also being discussed to add an additional radar, onSpitzbergen. to EISCAT in order to extend the viewing area furthcr into the polar cap. TheScientific Advisory Committee, supported by a special working group. considered the scientificexpectations and the potential configuration of 5uch a radar and the Council look opportune noteof these plans.

A few slaf( members len EISCAT in the year 1989; these were: the engineer Arne Björk from theKiruna site and the tape han<1ler and data analysis operator Dan Lindgren from Headquaners. Inthe spring, Dr. Cesar La Hoz finished his tenn as Assistant Director in Troms~; in his honour, aspecial colloquium was held at Headquarters in Kiruna. We all acknowledge the imponantcontributions of these persons to the operation of EISCAT. From spring 1989, Dr. GudmundWannberg became the Depuly Director of E1SCAT and in June 1989 Dr. Anthony van Eykentook the Senior Scientist position and Stefan Heck the Radio-Frequency engineer position at theTroms~ site. ToriU Johansen, Inge Mantala, Lena StAhl and Kari Tuovinen were other staffmembers whojoined EISCAT in Troms0 and IGruna, respectively. In general, the Slaffing levelhas been stable, with 35 persons in post during 1989. The total budget outeome was at a level of16.72 MSEK, recurrent chapter, and 2.60 MSEK, capitai investment chapter (Fig. 2).

I thank Tony van Eyken for compiling and editing this year's Annuai Repon; it is shoner, andless colourful, than those of recent years but this should not be taken as a sign of reducedoperation or scientific output (on the contrary, see pages 13-40 and the 59 papers, and 34 otherpublications, in the reference lists, starting on page 43). Rather, the reason is a budgetary onesince we have to share the costs between this 1989 Annual Repan and an EISCAT Brochure,which is being printed at the same time. We hope that both publications provide a suitable andinfonnative overview of recent operations and science as weIl as the general scope of EISCAT,leading the way inta a successful next decade.

Jiirgen Röttger

01he. 04

30.5

O--;o o" -"::0--"::0--""0 ""

Capital Investments lMSEK

. , 7. ;'-.-'"1-, .r' ';. -••

.~-"',~d

".~I",,,,e..

VHF A~le~~a

UHF "nIeMU

----- ~~- --Recurrent Operating Casts

1916 MSEK/year

1918 .. ..1980 ..1982 ..

,n

\984 ", .. ,1986 .. ,

,n

1988 '"1969 ,"

O • " " "Fig.2. The yearly development of EJSCAT's recurrellt budget (lejt) and the distribution oj theaccumulated capital investment (right).

10

EISCAT OPERATIONS IN 1989

Common Programmes1115 Hours

Special Programmes1157 Hours

F'<IrlCe401 37"10

CP l 22

CP <' 19'~

Sweden8J 8%

UOIled K,ngdom271 25%

EISCAT57 5"'"

Gelmanv188 17%

F,nlana121%

'"

"

,

,. "~, _ U. M'_ o' Uh' _~. N' "' "..."' '".

:'00

_ t,"".. (ISC~T _ hO'." _ G."••• ,

" •••,._ ".... II..... "'.,....

fjg.3. Total EISCAT Common and Special Programme operations in 1989, and distribution ofprogramme time by month.

EISCAT operations (Fig.3) throughout 1989 again placed heavy demands on the systems;nevenheless, the diligence and professionalism of the stafr at all the sites ensured a very highlevel of system availability. as revealed by the chans on this page. Activilies were almostequally divided be'ween Common Programmes, top left, and Special Programmes, top right. Allseven Common Programme modes (see descriptions on page 12) were used this year ~ thoughCP·6 only in the fonn of tests.

Operations were weIl distributed lhroughout the year. lower left. though with the usual summerand winter peaks. The welcome appearance of dual radar operations. for bom CPs and SPs. inDecember marks the culmination of much software and hardware development and surelyindicates the trend for the [uture. The seasonal peaks are primarily caused by extensive SpecialProgramme campaigns. lower right. This year. there were several substantial campaigns duringthe wimer months, and a large collnborative Polar Mesosphere Summer Echo study. invalvingtime from sevcral Associates. in the summer. Resuits from same of these campaigns aredescribed elsewhere in this Repan.

""

COMMON AND UNUSlJM, ;'IU)(;H AM MI<: Ul'~:RATIONS AND",,,ALYSIS

:""J'IU~:J' f.ND I:;Xl:'T ~J·I·f,.tI'l' r..:NfI EXPT,'/ -lU1 ,," mi ~\l' -11l) "" '"' t'J, III l 1"11'1"111) ""

, .,)liMON ~"(,,t;XI\11HI:.' liA 'l'j., il 'J "9 U8-:tB ,UU'l' O!l-OJ. l tiO'!! Cp-2-D:Irl\~J -,)IJ"{)~ lOUT OY-06 13U'r CP-l-!

Il '! V' , ,1 " .\0', ,)I ; , l J/J'J '! ') o'·, l:) lOUT UI,l .;~ l HUT CP-3-E',l 'J 01' .oJ I, 'j! 1'1 02.-1)! l SI)'I ,. iJJJ J()'lJ~ 12U'1: 10-0'; 16U'l' CP-4-A*l. ') '. rl"/ "-." J'r 11l.· " lj U ~t,'l' Il 'I ,o,: ..'3 1 !lU'l' 10-2~ 14UT CP-2-D

'. j 'J ,I ),1 r II":' , " J 1(1"]' . ,; tl~ 11 11 lUu'l' 11-J(. JoU'I' (:P-l-IIl " ,,.' ! J 'I 'J I "r o ' - , Iblf'J' , , , 89 U-L'l lOar 1.J.-2JJ 16'U1' CP-3-Y·') " /I • dl oj 'Il , " j " .:J ]t 1/", j' i , .," , ", " .1

l, ,I< r, j, J , ,:'" ,. '}!l' !;" vA I. l' tt(Jb KA/1I18 • DATA 1989., - ". H,.! ," I ';I MHa , ,.J .: I) U, J'i' " , .V .'L(Q' , , ..: I , ;; 'I VI lO O~(J'1' lJ~"IO nUT UP-l

:' 'j U- (J .' .hl! n' n', " , IJlllj'l , l,"!, ]oj UL lQUT 10-,02 11 UT UP-1,,;1' u5-09 Q8U'!' u; il 0811'j' ." j -H'" "' '" ~(J u9IJT 10-20 !3UT UP-l.; Q'-05" 'jO 10p',' 00 ", J. 4(/'1' , '~. ., A' "' , O :! 'l l:t:UT 10-23 leU'r UP-lb y- Uti - UJ. J. 30:1.' u8-0.3 16fJ'l' ,'. ,- /ly " 01 U9U'r 12-01 12UT UP-l

i<l!fle 2. t/SCAl (.'0"""1'1' tUul U/lulu.rl I'foK"l1tU/l;; "i""."I,,",~ ",,j l/uto unlllysi~' o...er ...iew for /989. Marked{"fIl' u:,, imth',Hc World VtJY ulJt!ru/jOlu, [ur Il'hu.h the ri:.>ull., 1I,I\,t! (JI~(J b':ClI ~'cll/ 10 NeAR. Boulder,

Comlllon Prugr.unme Ollt, CP· L lIses <I fixcdltllnsmiuing llntenna, pUlIlling alollg Lh~ geuIlllignel.icfIeld lhrectioll. The lhree·dilllensionai ve!ocily andauisolrOpy in other paramelers are measured bymeans of the recei\'ing stations at K iruna andSodankyla (see map, inside front covcr), CP-I iscapable of providing results wilh very gvod UUll:resolution and is suitablc for the s\udy of sub~tonll

phenomena. particularly auroral processes whcrewnditiollS mighl change rapidly. On longl'r lilllt:scales. CP-I Oleilsurenlen{s support studies of I1lUrnaichangcs. such as lltmosphcric odes, am.! scolSQfmJvariations. Solar cycle variability will a!so be studil,;4.Jwhen sufficient data have been collccted.

('(II 'I mOll I)ru~ramme Four, CP·4, covers latitudes upiO ahn()S1 80 N (77'N in variant latitude) using lowdevalioll. azimuth beam swioging. CP-4 isparlicularJy suitable for studies of high lalilude1l1aSl1la cOllvection,

CUllI1l10n Pi"Ogmmme Five, CP-5, has been designedlu Sil il t~ objeclives of lower LhenllOSphere couplingswdies lt combillCS a lalitudillal sean with dctailedlIlea.~llrt:U1Cl\ls along the TromS0 llla~nctic field line.The prin.a.ry aim of lhis eXl>Crilll~ll\ IS to observe theU}'ll.llllics "r llil; m:ulral aLJlJosphere, whilel>IlllUJHiH""."I~ CXplllJlflg 1he Il,.;a! eJcctrodynamic\' 1\\ 11\ II h U,III

CUlIllllUll Prugraflune Two, CP·2, is tk:signcd II' .... tJ·Irll:asurelllc.nb; frufll a small, nljlid tranSlIlillcl <'Ulllil1. l(.1n, Olle aim is 10 idcnlify wave·likc flh'~II(IIll<':' ..,dl I';Hl;th;Hid time .scales COlllllafahle with. o, 1"'~Cf

LI •.'l" Ilie !>\·l:tfl (few ten km and ahotlt ten l!lillll!~~)

111,. l",:~h' v\·r~UIII erHlsj"lS of a four POSlljOll »(;111

",111"11 l:'; CUlIlpkIeli Ul ~'\ 1.,+llllh',~. Th,' lil,~1 IhrlX1'lj',lli'~lS f!lOIl ~ UI',!),)' \\111, I·CII-I,,.I :,;ulHh iUl(!:".",11 c,..~1 POSI\fUllS, I'.'tlilc lht j"udh IS .,hl(,,,;,l 1"lIl!tilt' IUdöllclic Odd ., 11-: leLl,'ivc" silc dlll. ,"uh ul.,"(·!I" ',. dil'l, lI-:i{ll,.;J ,I,.' ilY ""',bu",'"'' 1'1 '" ,i".I' <.',1. ,;

,",'1 .r" .. r ,

lo" I' 'r<lr"

, ' .. ,h'hll' l'i'll,!",',jIIUW,:s Ulle 111 Flve arc rUIl on theIII H' «Il! II 1 wo furIJI":' 1'i"llgfåIIllHl.:S ale lksigned1"1 lI,~,· wiil, lit,: VIIF S)'~IGl1l. ('{)1nmllll Proglamme·;1' t -I' {, !~ Ik~lgllClI f," 1\1'" "l\illltle Sludies, and, 'JJlllh,', l "'~l"'llllllC S",v"'ri, ('I' 7, 1(11' high aJtilude.1',ulI,,,L.lIly 1)0..1111 \VIII.!. \\',jlk. CI'+7 has been"1"'ld,cd <;ev,'I<l1 lltll~ III 191N, ItUI ('I~-/) has so far"tii, 1",';1. lUll illul,;gui!>CllfUr' 1.1-..duw, wiLh which,1 ! II Il i, .. ,I

.1, ,! I 'u 111"~""!I"H,-: k",,~ h":IlIit-fiw.:(I: UP·!.. 11 ,,',l,d ',fo ..... ,.\dll'mS (lViII.:!)' 1I:\\~t.J lhis year, 011

Il,. Ulll, ""hu'. iiI ,1\1111......:iu'" ·..,illl Polar Cap'\l'tS"I(llhlll ":""111.:'1, lJl'-! f", ;.ul<)I<l.1 nfl. alltl n~Jated

, I",h..~ '" .. l t 11'·\ fvf lugh tCSlllutioll s!xI(ädic E-layer.1' l ',1,,1 I'h,,,' Jl"lrJ,UIJ'''~S lire slllncO al slwrt

"1 1 'I 1I1i.Il>k gl<. lJl!ysll·lll t:ouditiul1s are.1 "i

l','I I "~Ill.'"

j, i 1,(I l.. l!"

"~o r, dl..,

, ,l lo" '11,,1"\" ·,IU,'"

if, III:UIl1o

pI" I" ,r ;1

,l,I" l'

"Il II. I11,'<"" ,,·H

,I 'l,l

", "i I l llt

Ol 111. 'II" I,

,"

,, ;.I

i", , ,

I

SClEN'l'IFIC RESEA.RCH

"'LlHh~1 'HllliC!\ ,,! ,l, .. IIt!c"·t<>l'lit;l\- ~U10l1ler

l~1 h,~·~ \l't.t.t' ""nl;1 "",...re Jc.l~dGd wllhllrc lIS('fl r Vlll .UIL! UnF W.,J'li·S. yieldc;d~;;'I!IC. ]I1'_lt. imji}.'IJl will the \.hd. ".... t.Cri!ötics ofl'l~ ...~ ~tll{~S. ·1·IJ~ ...t; ,111,rlg tl..'Jlt~S are nOl

dllt lo l:l.HlVtlllJUJHtl Itltohen:nt Sl:attef, buttlle final illit'!P' I,Jti,. I' nf Ihe ,scaueringlllc..:hi1\lIMll, and ll,~ gt"IIC;lilIJOIl rnechanismof l..I:e sCillIering rfltlguhmlies, causing thePMSE IS stil! UJlucdJc:.d. Using multiplebeam directions ;,l/lll Lhc newly devdopedfrequem.::y domain interferometry il wasfound lhal the scauering irregularities can belocalized in thin sheets. less than somehundred me!ers in thickness; these sheets canbe inclined away from the horizontal(van Eyken, C. Hall and Williams; Franke,Hoppe. La Hoz, Rielveld, Röugerr.

AIthough sllch inegularities, which are thecause of Polar Mesosphere Summer Eehoes,occur in the same altitudes around 85 km,and during the same summer time period, asnoctilucenl clouds (NLC), a clear relationbetween PMSE ,lOd NLC has not been foundexperimemally. The lack of carrelationbetween the occurrence of NLC and PMSEmay be explained by the characteristics ofthe nucleation process, which fanns the ieecry'aals causing the NLC, and Other factorsthat i,,;unlrul t1l\~ visihility of NLCs, such asviewing angle ::'111'/ Pill'III.le siu (Taylor et al..1989).

Ii is \'ery evidelll lil.ll tlU;'.IC b il prlmuunLetlfreqll~l1cy depen~bl\ of Ib~ PMlolE, i.l;;. Iheecho ilJtc:nsity i:. lIlllll. :.t/uflgc:J ,Il VI·lf lhatLLJHF. This w.: d ·lll"ll''1l",'I\"'d 1.y 1.01l1palillgLhe 'Il' I';fl!t'q l 11 Illt' !'hl"AT tJlIF.nOl ... il' 1.lIl,' • II' l \\'idl lllt." 40.1.) MHt.:

l:\/lIwJ! lJnlvt" PI'JI,lllle Radaf lnler-il'l.lll' "., tf lll'I·I} 1,111.11, Whl .... 11 h.ld liten't'CJ.' ,I ,t. Itl! ;, ';Ulllllio.;l I'JHM. IL is

t l, JUI'l!' :!tal HI,'l f!l.W Ol.~. ~calleri.lLg

1·,.iI ".1.1 IS !Il l il fl) (''''1,1<1111 tlleSe, I :.~·I ·11 (! ,lt:~~·, IdVI·1J. La Hoz,I lIal!, \<.o..:.lley :1.1.1 5,1,;111/.)

:)Olm; llh.;e>tit::i ,111. !Il l'lI:par:llioll to explainlhc- :sc.ltlcring 'UlJ irn:gtllarilY generalionmedWllisll1. TIk:>\., ulI:ompa.ss enha.llcedturbLJlenc~ ulle IU Sllpl.:r-saturat~d gravitywaves, all illtn:ase in Lhe mllbipolar diffusion

coefficiem ,~allsjJlg Iht:: electron densityflut.::tuations [O cxtend 10 slnaJh.:r scales thanin the ncUlral gas (Kellt'j. Ulwick, Rönger,1llhester, T. HaJ! amt Dlix; C. H:I1I), thefon nation of eleclru.lI duuus öLl"OUnct chargeddust particles enhanciflg the seatler crosssection (Havncs), enhanced ele"tron densitygradielIts which can OCCUl duc to increasedattachme:H and recombination or caplure ofe1ecrrons in the presence of lhin layers ofheavy posilive ions (Röug('r and La Hoz).The Ialter [hree processes work best in a veryeold environment such as the summer polarmesopause. More ex.periments, panicularlytogetheI' with rockels, are needed tounderstand the mechanisms behind PolarMesosphere Summer Echoes.

Frequently, pronounced velocily variationsare observed in the presence of PolarMesosphere Summer Echoes and theinlensilY of the PMSE eeho can vary with thesame period as the velocilY. Fig. 5 showssuch an event; immediately below the PMSElayer an atmospheric grav ity wave wasobserved with the same period of27 minutes. The maximum intensity of theechoes corresponded to the maximumupward velocity of the wave. It wassuggested that partic1e precipitation,adiabatic cool ing due to [he upward velocilY,wave s!eepening and wave breaking at themesopause all play a part in causing theseevents. Also, gravity wave dissipalian andbreaking can expiain why regular waveoscillations, which nonnally incrcase expan­t:.:ntially with height, drop sharply inamplillltle around 86 km (Williams el aL,1989; Williams and G. Jones).

Eneigelle solar proton ev~nls (SPE...) occurmOst frequenlly lhl1 mg Ilie sunspOtmaxiuIluIl. Tht:"e SPEs n:sult in a strongatld lung lasting l)-lc~i(Jl\ elci.:LrOll d~nsi[y inthe polar cap, which Cilllses enhancetl radiowavt:.: absorption known as polar capabsorpuon (peA). Tht:.: pre.sent sunspOlcyck is at ilS maximuul in lhe years 1989­1990. Several of these SPE:; occum:d in thelast yt:.:ar and were ubsen'ed wilh ElSCAT,mostly in Unllsl1?1 Progn..unmt:.: operations.

* Rcfel"CllCeS given withoul dates indicaLC work inprogress. or in press. Other~ can be round in lhcrcrcrence lists. SlaI1.ing on page 43.

13

"

•

-r--,(

~

1 Docembo< 1999

- ,_'" -+- ""."" -.- "00""..... '1>'''' __ ".,," -+- •.,.lJ\'

- ,,..'" - ... '»OU, -O- ""'''' ... ' .... Vf - ..,"" ...- ''''UT

-o- ''''\Il _h_ ""'"

""lIT

Fig. 4. Northward velociry profiles measured during PCA evellts with the UHF radar. Eachprojile is an average over 2 mil/Ules and is offset by 50 ni s·, to the right of the previousOnes. The sloping solid lines show the descending ve/ocity maxima.

The prolonged U·region ionization duringPCA events results in long series of goodsignal~to·noisennio data down to a1ritudes ofabout 50 km. These data seties have afsobeen analyzed to obsct've long~period waves.Jn Fig. 4, ln~rid.ional velodty profiles areshown, which were mt::asured with the UHFradar al an elevation angle of 45'. Clearly,very largt: velocity amplitudes and venical

""..

lIkm 66

77:

"

wave structures with descending phase canb~ seen. A colour representation of some ofthese results appears on the front cover ofthis Annual Report. The relationship bet­ween these strong velocity amplitudes andPCA events needs to be sludied as weIl aswhether they are relaled to 8-10 hour wavesuf to the semidiumal tide (Rietveld, Collisand Röttger).

Fig. 5. HeighHime COlllOurs of echo IIItellSity (lejt diagram) and verrical vetociry (rightdiagram) during the presence ojPvlar Mesosphere Summer Echoes measured 011 12 August 1988with the VHF radar. The stanred lines show the phases of maximum upward velocity. Theinrensiry varies over almost two orders ojmagniwde and the velodty varies between +f- 2 m s·t.

14

Radar observations dtlring SPEs showedincreased elecrron dcnsities down to 50­55 km, the lowest ionosphC:f1(" I,cights fromwhich signals have so far been detected byEISCAT. At these heights the ion ehemisttyis eomplex and negative ions fonu part of theplasma, partieu!arly at night when freeeleelrons ean attaeh to neub'a! species tofonn negative ions. Sunlight easily destroysmost negative ions and then' fonnatian istherefore most pronollnced at night. Thelack of data in the lower altitudes after14:30 UT on 23 October (seen on the frontcov~r display) is caused by the reuuction ofelectron density al sunset, even though theionisation rate due to the incoming protonsremained essentiaUy unchanged. Twilightobservations are particular!y important forstudying the behaviour of the negative ianpopulation. Increasing negative ian densitiesat sunset were detected through the in­creasing width of Ihe incuherent scauerspectrum as the solar zenith angIe increasedbeyond 90· (Rietveld and Collis).

Eg. 6 shows the diurna! variation of theelectron density, measured with EISCAT,and the absorption, rm::asured with riometersat Kilpisjärvi and Kevo. Detailed analysis ofthe time variation of the eleelron densityindicated that the aJtitudc regions above andbelow about 68 km were gavemed by twodifferent mechanisms. Changes above70 lon eould be explained by solar UVradiation interacting with high-affinitynegative ions (passibly N03), whereas below66 km the temporal variation of neutraloxygen species appean::d lO play thecontrolling role (Collis and Rietveld).

Under quiet ionospheric conditions (i.e.without any particle precipitation) theD-region can be modelled since the electronscan then be assumed to be solely due tophoto-ionization processes. Using a neutralatrnosphere model and all assumed solarflux, the equilibrium profiles of electronconcentration can be detemuned fromchemical medels. Using a D-region electrondensity profile measurt:u with the UHFradar, it was shown lbal a modification of thenitric oxide profile cOlIsiderubly improvesthe fit to the data. The dt:tluced nitric oxideprofiles were used [O sludy the effect of thesolar zenith angle. The profiles show peakconcentrations between 1.5 and 4.0 101S m-3

at 95 to 100 km and ahout LOD 10') at 80 kmaltitude. Such values are more represent~

ative of previous estimates during disturbedcondirions than of the quiet conditionsduring the EISCAT observations (Bums,Matveinen, Ranta, E. Turunen, andHargreaves).

801 ,-------,,,.......,-------"""7""""ta 100

110

~----=---'------::":::::::=:;

dB

Ffg. 6. Time series oj eleccron density,measured wirh CP-2 on 23-25 Oerober 1989,solar zenich angle (xJ and absorprion (dB)during a solar proron evem.

Most of these D-region measurements aremade with the Barker coded GEN-Ilprogram. The application of this particularmodulation scheme leads to range ambiguityeffeets, which can be minimized by means ofspecial correction procedures (Pollari et al.,1989).

15

E·REGION STUDIES

Studies of the E-region conductances havecontinued using CP-1 data. A method hasbeen developed to derive the energy spectraof the precipitating particles from theobserved electron density profI.1es at night­time when no solar ionization is present.This routine is based on a simuitaneous fil ofa number of 24 ion production profiles,caused by mono-energetic electron beams. tothe observed electron density profiles(Brekke. Moen, C. Hall, Pettersen andHanson).

JUNE 25-26,1985160

E 1250 UT-'"~ 120.c --.C'aJ

~ m3 sec-1:r:80 ,

108 109 WO 1011

1081250 UT

~, , , ,

-'" ,106

,Vl

,,~

,E

, , ,u ,L 10 4aJ~

Vl

~

102~

aJ

keY1

1 10 100 1000

Fig. 7. Upper panel: Particle ionization rateprofile during the period 1250 to 1355 UTon 25 June 1985. Lower panel: resultantenergy distribUlion o/ particle flux (full line)using the ion producrion rale proJiles in theupper panel. The broken line is the energyspectrwn obtained using the total ionproduction rare profile (soLar backgroundionizarion nor subrracred).

16

An auempt has been made to derive anempirical relationship between the root meansquare energy (Enn.) of the precipitatingauroral panicles and the Hall to Pedersenconductance ratio (R). It has been found thatfor values of Ennl less than about 15 keY thisrelationship can be expressed by anexponential formula as follows:

E=. = A exp (R/B)

where A and B are constants derived fromthe data to be 2.22 +/- 0.30 keY and 1.66 +/­0.35 keY, respectively. These derivedresults are in reasonable agreement withMaxwellian energy spectra.

During day-time preclpltation events,however, the solar ionization contributes tothe conductances as derived from themeasured electron density profiles incontrast to the situation at night-time. Forsuch day-time events, a correction has to bemade for this background ionization beforethe routine can be used to derive the energyspectra of the precipitating particles. Amethod has been developed to achieve thiscorrection and residual ian producrionprofiles for (hese day-time events are ratherheight limited and usually situated below110 km (see Fig. 7). The derived spectrafrom these profiles are narrow banded withroot mean square energies typically largerlhan 20 keY (Moen, 1989; Brekke, Moen,C. Hall, Pettersen and Hansen).

The Rocket and Scatter Experiment (ROSE)project was a coordinated study of theauroral E-region using rocket-borneinstrumentation, ElSCAT and STARE(Scandinavian Twin Auroral RadarExperiment). A major scientific objectivewas to investigate the discrepancy of derivedDC e!ectric fields from ElSCAT andSTARE. EISCAT observed above the rackettrajectory, the common volume being at analtitude of 150 km on the same field line asthe rocket apogee, during four ROSE flights.E1SCAT delemrined E-fields above lherocket and at the same time observed theregion of E-region instabilities in the Troms~

beam.

In Fig. 8, the series of arrows gives themagnitude and direction of the electric fieldperpendicular to the magnetic field lines,Eperp, as a function of flight time. The rocketdata are measured along the trajectory

,.~o....,.,"~o:-::,,;;;-o"7.,,;;-,-;,Ö;,,;--;,,~o~,,;;;-o-,;;:,;;-. -;,Cc,,;;--,,;;,,;-c;!~u·~fLICHT TlI.tE: ("j STAllT 2:1 ~2 00 OT

A modified retarding potential analyzer wasused on the ROSE payloads for measuringthe electron density fluctuations in the range

Fig. 8. E/eeeric field measurements, AC andDC, from ROSE payload nlunber 4 and DCeleerrie flelds dedueed from E1SCAT andSTARE measurements.

The optimization of incoherent seauermeasurements in the E~region has beeninvestigated. If the power and duty eyc1e arefixed, then it is possible to improve thedetection aeeuraey by using different kindsof eoding. However, the aecuraey of themeasured autocorrelation funetion eannat bebetter than a eertain limit. whatever type ofcoding seheme is used. The aceuracy ofalternating eodes was eompared to this limitand a proof of the limiting accuraey based onlinear statisrieal inversion theory has beendeveloped (Lehtinen, 1989).

The fme time and height resolution madepossible by the introduction of thesealtemating codes has led to the most aeeuratemeasurements of E-region parameters yetaehieved using ineoherent seaner radar. Forexample, during the ERRRIS (E-regionRocket Radar and Incoherent Scauer)campaigns of 1988 and 1989 many hours ofobservations were made which could beanalysed with time resolutions as fine as45 seconds and height resolution of 4.5 km.

10-200 Hz which are created by the E-regiOnplasma instabilities. Enhanced fluctllutionswere observed in a narrow heighl range, 90­115 km. on the upleg and also on thedownleg, in agreement with theory whichpredicts that the majority of the power willbe concentrated in the lower frequency band(10-100 Hz). The relative fluctuations of theelectron density. Ne• averaged over allfrequencies are in the range of 2-4%.Similar results have been reported by otherauthors. The instrument was also capable ofmeasuring a relative electron density profilewhich was calibrated with the help ofsimultaneously measured EISCAT electrondensities (Schlegel).

5uch data allowed a systematic study of theenhancements in electron temperalUre. Te'observed between JOO and J20 km duringperiods of high electric fields. The fine timeresolution demonstrated that the electric fieldstrength varied substantially over short timeintervals. On one occasion, for example. theelectric field strength aJong the Troms~ fieldline increased from 60 mV m-l to180 mV m-l in about 90seconds. and fellback to 60 mV m-l in a further 90 seeonds.It is clear that previous electric field strengthmeasurements, typically averaged over aboutfive minutes. would misrepresent the truerelationship between eleetric field strength

"

'"

"

LOU 101o

80 ~<

'"o

ROSE F'4, ELECI'RlC fIELD, FEB 09, l!lU!J<00 r-~~-'--~-,

',.t: ELECTklC F~":(CllANN~L 1) ~

(northward from ESRANGE) and thealtitude is indicated by the dets. TheElSCAT measurements are one minuteaverages. The STARE measurements areattributed to an area at 110 km altitude justbelow the .pogee. The EISCAT and rocketE-fields .gree very weil, while the STAREresults are smaller in magnitude and arerolated, anti-clockwise, by .bout 15'. Theoccurrence of AC electric fields or plasmawaves is limited to an altitude regionbetween .bout 90 and 115 km. The width ofthis region, and the wave activity, increaseswith DC electric field strength. The lowerpart of the activity region is dominated bysrrong low frequency wave fields,presum.bly c.used by gradient-driftinstabilities (Rinnen).

300N

=-

17

1500StuLiies L)f the dislurbed auroral E-regionwere <llso made using the Dynasonde locatedal TroIllS0. A comparison of the electronIknsirit'"s, Nr' mcasured by the Dynasondewith sil1lull.lJlWl1S EISCAT measurementsdt'fivl:u fiOlll the rouline analysis ofC0ll11111111 Programl1lt: data showed that thell)lh.::~~IlIf;_l1ions tnt:-ilsured by the ionosondeW\'rl~ ,lflen a l"clOl' of 2 or 3 times greaterthilll lill.: ;lvt.fage v:\llleS given by EISCAT.Il is sug1;c~led IIHH, lll11.ler the influence ofstwIIg t::leclric field s, Jarge variations exist inthe E-fegHlI1 cJectron concentration with,,111,111 sell\: .·.izl.'::s. These lead to biased,.:slil1laICS {ll N", especially when the data are;H/t:raged over perioJs of a few minUles(Wright. CoJlis, Virdi and Kressman) .

USt'1\1 hao; mat!" rrgular observations ofphlslHa vc1ocily, :Il heights between 101 andIJJ km. for llli.tllY years. After correcting forthc cftt'CI or Ibe e1ecrric field, as measured inthe F-region, il is possible to derive thevariation (Jr l1eutral velocity over the sameht:ight range. These measurements are bestmade during quiet magnetic condilions, and14 uays during the period of sunspotminimum between 1985 and 1987 weresdectcd for this purpose. The measuredvelocilies displayed diurnal and semidiurnailidaIoscillations. The diurnai tide showedconsiderable day-to-day varialion in bothamplitude and phase. The semidiurnai lidealso varied in amplitude bUl Ihe phase ateach heiglH was fairly constam from day today. Relow 120 km the variation of phasewith hdght indil:ated:J dominant (2,4) mode.Above 120 km the variation of phase withhcit'.lll is ,)lowt:i' whidl suggests that at theseI:eighls lli~ (2,4) mode is :Jttenuated but the(2,ll tnf'tle. is still growing with height.l V;:di ami \Vil!iarns, 1989; Williams andVinli Il.~t').

lt was possible lO makt: :otringent tests of thevariolls tht:-ories proposed to explain electronheating in the E·region. including the modeluf p1aslllon·electton interactjon proposed byRobinsorl. Though several of the parametersemployed in the model. such as the variouscoefficiellts of electron cooling, are not weilk.nown. the agreement between thepredictions and the observed data is verygood (Williams. G. Jones, B. Jones.Opgenoorth and Häggström; Jones. R,Schlcgd, T. Robinson and Häggström;Häggslrölll, Opgenoorth. Williams and G.JOlles).

."

I "EI':".U.1 l:!

.' .~,h1 •• ~ .. ':.

........,.~:•.!.' r.-l' ..1.

~I'(I

[lSCA! (Il 23/03/88 1')00 210J III

2000 ,--- --- ....---~ ,

h ~ IlSko,

llseAI fll .'~'!lr··;- 1:·,-,(1 'I"" III

Fig. 9. Electron remperarure, T(, observedar 106,110 and 115 km, 011 23 Marc1l1988,plotted against the electron drift veloätycorresponding to the observed electric field.The broken line illdicates the relationshippredicted by RobillSOIl in 1986, correctedforthe estimated neutral veloätyat each height(Jones, B., SeJllegel, T. Robi1l.\{ln wulHäggström).

and Te enhancement. Special care wastaken to identify any spurious dala caused bytransmitter failure. antenna movement orsatellites. and a correction was made for thetidal motions of the neutral atmosphere sothat the effective electric field at each heightin the E~region could be detennined. Theobserved relationship between Te and theeffective electric field was therefore morereliable than any previously obtained (Fig.9). This is reflected in the small scatter ofthe data about the means.

18

Similal n:sults lor tllo,; iJlCI'H.llOilJI Udb ''''''''11':obtained using tho,:; ERRRIS U;:Ilallase fur aperiod at th~ Le.ginnillg of Ule 1988 whichwas geol1lagnetic;:IlIy ljulet (Hg 10). Laterin me campaigIl, ho..../ever. (.:onditiulIs WCft:

dishu'bed and Ih~ lidal illooes no lOllgcrob~yed the snille; pauern (Huuskont:n. VirdJ,G. Jones and Williams).

ambic:nt illcta1 alutu cOilcenU"dtion being ofthe order of lOll IIr3 at 105 km altitude(Nygren, Lanchcstcr, Huuskonen, Jalonen,T. Turunell, Rishbcrh jJnd van Eyken).

01 .'•

'"

"

"..

.., ~''''.

""

' .. '"

'"

..

,~ 'I," .,nl''''\ .

~'I."',\ 151.1.,,\._'._.. _'- --~~~ _.~~-- .100_·

'"

Fig. JO. The fltted phase of the semidiurnaicomponen! of the meridional neutral wind onflve successive days between 2J and 25Marcll 1988. Tlle plUJse profile for '"e bes'­jitting mode of the semidiurnai tide is shownin eacll case (solid line) with thecorre~pondjng mode number in paremhesis.The dashed lines are extrapolations of themodet profl/es beyond the fltted height range(Huuskonen, Virdi, G. Jones and Williams).

,.,

Very gooJ IneaSUreltlCnts of Spol'<ld.iL: E (Ei

)

layers, and of wave activity in both the E andF-region~, were obtained USillg Ihe SPOREexperiment in the summers of 1987 \i.nd 1988(Lanehester et al.. 198Y).

Thl:.' w<lve specln1 ShllWIl in l::'·ig. 11 \vel'~

llbt,uiled flom the data llf 10 Jul)' 1987,when stJ:öllg partielc precipita.tioll acted as allul'egular energy input, making the wQvepaIterus rather disordered. 1ncre is evidellceuf reflCdiulIs al cel1ain leveIs, and of lIOll­tillear inleraction between atidal wavc andatlTIospheric gravity waves. Followillg astrong burst of particle pre<.:ipitation, an Ellayer fonned al 2100 UT; the metal ionsappear to have been produced by chargetransfer, from molecular ions, rather than bydirect jonisation, a tentative estimate of the

".

Fig. J/. Power speClra from ihe F.region(rop) and the E-region (/ower /Wo) SllOwiflglhe presence 0/ Wllves of severa/ differentperiods (Nygren, Lanche::iler, Hutlskoflf!fl,Ja/onen, T. Tunmell, Rishbelh andvan Eyken).

19

A typical sequentiaI layer event, observed inthe aftemoon hnllrs, showed the Cffectli ofinterfering tidal and gravity waves (Fig. 12).The El layer was composed of a mixture oflight and heavy long lived ions. It eventuallydispersed during a rapid upward surge of ionvelocity; the atmospherk waves could befollowed lhroughoul the E, F1 andF2-regions. lt is interesting that the so-cal1ed'corkscrew' mechanism does not necessarilywork and. at least in this special case, the Ellayer related to the tidal wave did nottransport the melanie lons to Iow altitudes.The layer was destroyed by rapid upwardmotions duc 10 cfumging wind system andthe metallic iOlls were evidently thenn::distributed to the upper parts of theionospherc (Lanehester el al., 1989).

The derivation of coUjsion frequencies wasfurther refined using ve]ocity measuremenlsin two directions. Heighl profiles of two ionvelocity componenls are measllred

sequcnlially in vertical and easlwarddirections and the e1cctri(.; field Ueterminedfmm trislatic velucilY observations. ThecoUision freqllency is [hen found by solvingthe momentum equ81ion. lJsing incoherentscatter data from August 1985, il was foundthat the usual modet v!t1ues of coUisionfrequency might be tOO 10w. Pmctically allthe high spatial resolution dala available inthe EISCAT dalabase was used in a furtherstudy of collision frequencies. The resllhsindicatc that the MSJS·86 model givescorrect col1ision frequencies for July, bUlunderestimales them for February andAugust. Temperalure observations in theE-region show evenHa-cvent vmiationswhich exceed thase predicted by theMSIS-86 mode!. The eleetrlln and iontemperalures are 800m equal at 110 kmahitude. but in a narrow region aOOve110 km the ion lemperature slightly exceedsthe tlectron lemperalure (Nygren et aj.,1989; Huu,kollen 1989).

KEY

140

130

120 • so• 25• O110 --25

E I!!l-SO

-'" 100 -1 S-UJO::>l-I- KEY~ 140..

130

120 • so• 25• O110 --25

- SO

100 --75

1900 1930 2000 2030 2100UNIVERSAL TIME

Fig. 12. lnterferellce efJeclS caused by gravity waves propagaling in the E-region. The diagramsare produced byJUrering lbe derjved velociry jields Wilh bandpass filters centred on gravity wavcfrequencies revealed by Gl separare speC:lraJ analysts.

20

AURORAL ARCS

The UP-3 code was used to abserve thinionization tayees during pulsating auroras atthe same time as the CUPRI radar detectedextremely intense backseatter echoes withlarge Doppler shif",. Such echoes could beproduced by current driven, collisional,electrostatic ion cyclotron waves. but otherpossible mechanisms cannot be discounted.lon temperature enhancements of up to100 K have also been observed at altitudesdase to and even below 110 km, indieRting{hat exueme healing processes take placewithin or near these [hin ionization tayees.An equivalent electric field of 200­300 mV m-I would be required to producethe observed ion tcmperature enhancements.but EISCAT detected convecnan fieJds nogreater than 10 mV m-lon these occasions(Fig. 13).

The currenl hypothesis is mat a beam·plasmainstability might be responsible for both thethin layers of ionization and the luminosity,the ionization being caused not byprecipitating particles but by suprathennaiionospheric eleetrons, accelerated byinstability generated ion cyclotron. andpossibly ian drift, waves.

E-region measuremenls made with 100 mstemporal resolution and 1050 m spatialresolution were campared with optical data.Electron densi ties ealculated from the opticalmeasurements correlated well with the trueelectron densities measured by the EISCATUHF radar at 110 km altitude. Aurora! andeleetron density pulsations were observed tooccur together. During these pulsations, theenhaneed electron densities below 100 kmcould be caused by two different Maxwelliandistributions with energies of about 2 and10 keY (Kaila et al., 1989, Kaila andRasinkangas, 1989).

As mentioned earlier. shon Iivedintensifieations of the auroral zone electriefield have been found to be mueh morecommon and intense than previauslysuspected. Most of these intensifications areassociated with the passage of auroral arcs,correlating partieularly with their leadingedges. Enhancements of the eiectric field tovalues about 100 mY m· l on the equatorwardedge of evening sector arcs and on thepoleward edge of morning sector arcs are, infact, very common. It appears that the

sharpness of the features (several 10 km).and low electron densities in the affeetedregions. effectively eoncealed them fromradar experiments less optimized than thealternating code teehniques now used. Suchelectric field enhancemenrs outside auroralares bad earlier been reponed onlysporadically by Tocket studies and seldomincluded in theoretical or statistical modelsof auroral are electtodynamics. The eleetricfield enbaneement outside many auroral arcsis probably strongly dependent oniOl1osphere-magnctosphere interactions. Ifthe configuration of the ionosphere­magnetosphere eoupling allows a eompleteeaneelling of meridional eurrents within theare, by polarization effeers, the fieldenhaneement is not observed. However,when eonsiderable field-aligned eurrentsexist at the are edges, an eleetrie fieldenhaneement at one edge is a naturalconsequenee of eurrent continuity in theionospherie and magnetospheric portions ofthe three-dimensional eurrent system(Opgenoorth, Häggström, Williams andG. Jones).

F·REGION STUDIES

Simultaneous EISCAT and Fabry-PerotInterferometer (FPI) measurements havebeen used 10 derive the ion-neutral collisionfrequency in the high-Iatitude F-region. Itwas found to be consistently lower. by afactor of about 2 to 3, than the eurrenllyaecepted values. a result appa.rently atvarianee with similar measurements atArecibo whieh suggest an increase in thecollision frequency. Standard methods wereused to derive the thennospheric winds fromthe radar data and these were compared withthe actual measured winds. First orderagreement was quite good but largeexperimental eITOrs make a quantitativecomparison very difficult. and sueh methodsshould be used with caution. An analysis ofthe errors associated with this methodsuggests that it is very diffieult to deriveneutral wind vectors from radar data atEISCAT's latitude (Farmer, G. Jones,Williams, Moffett, Samson, Horne. Rycroft,Lester and McCrea).

Coordinated observations by the EISCATradar and the MICADO Miehelsoninterferometer, located in Sodankylä, wereeondueted for the flrst time during the winterof 1988-1989.

21

125 -~"-;"-:"'"'T-:=,~_.~

--- :-

tOO-300

t25

•

t,~,O (m sl

Vi

300

MICADO tncn')uremcnts of neutraltemperature ano wind were made using thered OlD line in the F-region thermosphere.Tht COIllpariSOll was (;ollducted between themeridional compOllen[ of the neutral windmeasured by MICADO and that calcuJatedusing EISCAT data for vertical ion drift,electron density and electron and iontemperatur~s. Il was found that, duringactive periods, the venical neutral windmeasured directly by the interferometershould be illciuded in the ca1cuJation of themeridional neutral wind from EISCAT data.During quiet periOl1s however, when thevenical neutral winds are small, thecomparison could lead to an estimate of the0+/0 collision frequency (ThuiJlier,Lathuill~re, Herse, Senior, Kofman, Duboin,Alcaycte. Bariier and Femanari).

In order to fit incoherent seatter speclra forion composition, il is usually necessary toassume that the different ion gases have thesame line-of-sight temperature, Thediscovery of anisotropic, non-Maxwellianplasmas means that this assumption is onlyvalid for one beam angle to the magneticfield,54.7-, Observations of a strong heatingevent at this aspect angle have shown that,within two minUles of the onset, the ion gasat 275 km is converted from predominantly0+ to predominantly molecular ions,

Ne iI3

-. _.

-,

1 2(10" m·')

---=---=125 -

100O

--",-="-

100i,-O

t25

r

(K)

Te

400

- .......:-'-.~,.; 4"'''_•~,~ ·,l)\·tl

''''o l' \ " ..-- ··-·---1./

-=-

fig. /3. E-region altitude profiles of field­aligned ion velociry (positive upward)eleuron density, and electron and iontemperatures derived from UP-3-like datataken ar 0341 UT on 3 March /988. Two orthree thin ionization layers can be seen(secomJ panel) with associatedenhancemems of about 50~75 K in bothelectron and ion temperature (lower panels),

Fig.14. lon temperacure as afunction ofioncomposition for a major ion heacing evem on16 December 1988. Conversion frompredominancly 0+ ions to predominamlymolecular ions (Jccurs as the ion cemperaturerjse~ from 2000 K to 5000 K wichin onemil1uce (Willser, Lockwood, G. Jones,Rishbeth and Aslljord).

tOO

O (Kl 400

'<"l' -o

,. IlL..

" '>1 """}1 ~"')O

, ~q 00-'11 4'i 30

• '1 ~1 lO-OI !lO 00

, 'h "n-I)' 50 10

, -:O'c;;--;;;cc~(> IOC 'lo IJO'!(. .J', ~\'

'. >~~ !O ~".,~,c ... "

22

Tram.~o

//'

o

o oo o

oo

, , ,

"'" ""'" '''''',>

oo o

o ...~...... o

.... ~ ~

o o o o0_

oo~ o oo

o

500 ""'" '500

_ "lOO

".~ l~OO

o~" ""'"~lOO

o

'''''' ,.~

_2000

"~"""•

""'" o

500o

''''''

newexpressians for a multi-companentneutral background, for arbitrary directionsof observation and for an effective centralforce appropriate to the callision processwere calculated. The drift dependence of theion temperature (derived from the statisticalanalysis of the Troms~, Kiruna andSodankylä data) was in good agreement withthe rheoretical curves for a bi-Maxwelliandistribution of Ot drifting in a neutralatmosphere consisting of 80% O and20% N2 (MSIS·86), with resonant chargeexchange collisions between Ot and O andpolarization interaction between Ot and N2.There was no indication of NOt dominanceat the F-region maximum during these events(Glatthor and Hernandez, 1989).

IJ- n·-1I5. 25-0J-86. 08-04 -BG. 29-07-86. 12-0!I-M6

''''''

Fig. 15. lo,~ temperature at 312 km allitudeas a function of ian-neutral drift perpendic­ular to the geomagnetic field, with fiuedcurves (solid) and theoretical cltrves forMaxwellian (dashed) and bi-Maxwellian(dots) ian velociry distribwions.

PLASMA~D is a combined ion line/plasmaline program which uses the CCD specn-umanalyzer for the plasma line measurement

Fig. 14 show:"! rhlj lun compl'silion as afunction of ion Icmp,-r:.JIUrt al Ihl:: peak of theheating evenI, deriwll Llsillg the second ofthese methods. In each post-integrationperiod, the dala point is in generalsomewhere on a line detem1ined by non­Maxwellian filS [O the observed spectrum.The limits of that line are set by the ianenergy balance equ:.Jtioll, usmg lhe range ofassumed mean neulral masses 21-32 amu (ifthose limi[s are elose logeIher rhe line isploueti as a poilll) !'or some pf'oods there isa range of v<tlltcs. \\ llicl! reflecls uncenaintyin the assuJncll l"nean mass of the neutral gas,but the observe<! "'pcLtrulll wic.lth consn-ainsthe true point ro Ii,; on the segment:; shown.

Theoreticlll l'olhsiOll modets predicranisotfOpil: illn lempl.:t1Itun;s il' !here IS a nettdrift velcx:ity bttwt"l:.l\ the lOn~ a.nd theneu[Tals. bve l'Vt:ll!1, with Idali\'dy suddenand strong in....:rca:;t·~ 01 the ion driftperpendit.:ular III the gcomngnetic field,found in EISCAT Cl'·l-F data sets, wereanalysed to illvesrigat~ the <lnisorropy andcollision proccso;. In:1 slatislical analysis ofthese evcllIS (Fig. I5), the ion rcmperaturesand ion ruin velocilies from the F-regioncommon VOIUlll~.•1[ J 12 km .:ltltwJe, werecorrelateJ. i1ecausc ollhl;; CP-I-F geometryand becallSe the ion drifts remained be10w1500 OJ S·I, a bi-Maxwdlian was as~umed tobe a good nppruxim<lliotl of lh~ ian velocitydistribution and O, 10 0-: lhe dominant ian atthe F~region tnaximum. For a theoreticaldescriptian tJf 111,--: ~dll"',jlr\)rIC i(1Il hearing,

Il can be seen that. irr~spcctive of rhe neutralmass, a de'lf {;onver~jon la predominantlymolecular ions OrCtlfS as (he ion gas isheated. Sut.:h il Ctllllpk t~ tOllversion to amolecu1ar iUII gas dOt"5 1101 ilppear [O be inagreemenr with plIblished rate codficienrsfor the relevant dlcmicill reilttions (Winser,Lockwood G Jones, [~ishl>eth and Ashford).

The dala <ulalysls alluw.• for !hr: distol1ion ofthe disrribwioll\ t.f l,f' uf-";,·h vdcX"ilY forthe two sep<h·M\~ I(m POPI111Id"". The ioncomposition i.:i ~\hllll~ll' d in tWiJ ways: rirstby fiuing SYlllh\;SII..'..;J ~PCL:lfcl for a lwo­species non~r-.'laxwelltilll lon gas to theobservetI spectra; and secundo by defmingthe mean ion mass ~\tlli(e<1 to make theobserved 1011 lemperalure (which is directlymeasured al the aspecl anglt:: u...ed) consistentwith a simplJilr'u form of 1l1~ ion energybalance equalion.

23

Fig. 16. Yl and Te from a combined ionline/plasma line fit (dashed curve),compared to temperatures derived from astandard ion linefit using the E1SCAT modelcomposilion (full curve).

880610 1120-1148 UT

K

K

,

Te

Tj

2600

1200

2200,

1000

•I\

/\

/\. ,/

./200

220

240

200

220

240

E-'"

t­:r:CJw:r:

Since the ion thennal velocity distribution isanisottopic, so too is the F-region iontemperature, lon temperatures paralIei andperpendicular to the magnetic field aredetennined by temperature panitioncoefficients ~r~ und PJlCry By exatnining theresponse of "Ii paraBel to the magnetic fieldto increasing plasma velocity perpendicularto the field. estimates were made of Pl'!'nt andl~~rp for the F·region and the vaJ'jation of131"". with height was examined (Fi~. lM). IIIthc: upper F-region the calculatoo values ofp ... agree with those expected for resonantcharge-exchaJlge collisions, whictl arerl\rt'.ded [O domin3le ut these dliiludes. AIW(sisltllt inclease III p141'1 with ho;:;iglll wase·,(.Juhslied, which is bJlieved 10 lie lJue tuf!l~·. jm;reasing inf1uelll:e of iun-ivll coUisiOllS,\' Illdl (tel lu ut:l:re.lse the: anisurropy of theItlll 111I:f111:\l disu-lI.t.li<':J1 :lIlJ lllt.fC.ISC (ht:!1,ht·p.:I;dlel compom:nt of 'f" TI1~

InJhu:u..:.c of tht: jon·jon collisioll fU~<luent,;y

" .. f\I"'" it1I~~lICC:;'i :1 1~llI(ll~rotufe 1~1.:1'\.·!ldelH;~lo! UI'; 1';ll111JU\1 !llll' lIul1 WhlJM:: Ifl'J_l\lrl.anceI"Ullll'! h,·,jn r(,l.\IJ.!,lli;\~d l'revion.Jj

l )".....1' JOO t:ast:s of iOH-friclional heating havelx:cn idtlltitied from a tutal of 1250 CP-!alltl CP-2 observations. The temporallbstribution, Fig. 17. has a peak nearmagnetk midnight with approximately equaldistribution between the regions of eastwardand westward ion drift. A close connectionwas noted berween frictional heating and thepresence of auroral boundaries, implying thatauroral precipitation may be important indetermining the structure of frictionalheating in the midnight sector (MeCrea,Lester. T. Robinson, Wade and T. Jones).

and the correlator for ion line dala. Therc;~ults have been used to dcrivt O·l'llmposition profiles in the F-regiull belween2lJlJ and 250 km by the lechnique introoucedby Bj~rnå and Kirkwood (l9~8). Thesp,,·clfUm analyzer provides plasma lineswilh ilnproved altitude and fft;lluencyIcsolulions, whicil is important fur thelkilvatinn of accurate compositiofl Vfofiles.. , !l\~ O'" content by this methoo <tjlplied totl"IGl suunnef· time dilla was gcnclJlly lowc;rdlol" !,fcdi~k:d by nIe mSCAT COJl1IJ\lsiriUlllll- ... Id, with the 1l1,):..1 sig,niticili1t t.1t:'Vhuiolls.11 Ilie "1'I)o;r ahitudc:~ (Fig. 16). Tlit cltl:lfOlIj, 1111:lrI.llIHl·S denv...... 1 u..;ing rht: ~\lllll't)sitioll

Plt... ld lIIc unuerc!>limtiotc:d by up 1./ 15%ll'Jt'c1l1k~'~1 iHld l.a lhii)

Occurence of Ian Heatlng Events agarnst Timelon Temperaturs Enhancsmsnt of lOOK ovar amblsnt lavalCPI and CP2 Experiments, 1985 and 1986 Altitude, 312.0 Km.

'00

90

•u,"•

"",u 7Duc

•m "•",• 50u

"•n.

"30

"10

O

11.00 \~.oo 16.00 18.00 10.00 21.00 00.00 01.00 0/0.00 06.00 06.00 10,00 11.00

Fig, 17. Percentage occurrence of ion heating events, as afunctiofl of UT, for Cp·l and CP-2observations during 1985 and 1986 (sunspot minimum).

Strong upward ion flows in the high F-regionhave been found to be associated wilh strongelectron heating during low energy particleprecipitation. Continued work on enhancedelectron temperatures in the topsideionosphere has resulted in a fundamentalchange of view regarding the electron energybudget during active aurora. According toearlier understanding, strong convectionelectric fields and collisional hearing byprecipitating particles (mainly viasecondaries) can account for the totalelectron heating in lhe topside ionosphereeyen during disturbed conditions. However,a detailed investigation of EISCAT datacombined with theoretical simulations oftopside heating by panicle precipitation hasshown that such mechanisms do not accountfuUy for the observations. (Wahlund andOpgenoonh, 1989; Lilensten, Fontaine,Kofman, Lathuillere, Eliasson and Oran).

Fig. 19 illustrates the good correlation foundbetween strong enhancements (up to 6000 K)of T, in the upper F-region (above 300 km)and enhanced electron densities in the lowerF-region. The altitude just below 200 kmcorresponds to auroral precipitatian atenergies of the order of a few 100 eV. Adetailed analysis of Te altitude profl1esshows that the main heat souree is locatedabove 300 km, and often even above themaximum observation altitude of 450 km. Itis therefore unlikely lhat the electronprecipitation is directly responsible for theobserved temperature increase. On the otherhand, satellite and rocket observations ataltitudes below 1000 km indicate a goodcorrelation between low energy panicleprecipitation and plasma waves in the upperhybrid band during active conditions.

25

." •,,• .', ..•• ,, ,

,, ,, , .'.• •~ ..,-

_1-~-c:--.c,---:.,--~DI .~ ., •• G. ••

,........_, ..'.," .......

-- ..."',........."",•••-- 09"" ........... ,

--.-- .. ",,,,,",--

Fig. 18. The allilUde variaIian of P",•• fortwo days. The dashed lines include acorrection due 10 the ion-eIecEran heat fluxduring ion heazing evetlts caused by thehigher eteceran temperature.

The amplitude of these waves is commonlyfound to be in excess of 50 mY m-l. Suchwaves could easily provide the requiredheating rates tO produce the Te altitudedisoibutions observed with EISCAT, even

when anomalous collisions are included(Wahlund and Opgenool1h, 1989).

During disturbed conditions the temperatureof electrons in the F-region above EISCATis affected by several factors including solarillumination, panicle precipitation andionospheric conveclion. During sunspotminimum, however, eonditions arefrequently very quiet and eIeelronconcentration and temperature depend onlyon the solar flux and the ratio of moleeularnitrogen 10 atOlnic oxygen. As this ratioincreases, the rate of production ofphotoelectrons by the ionisation of N2increases, but at the same time the 0+reeombination rate increases sueh that theconcenlration of thennal eleetrons decreases.As a result, there is an anti-correlationbetween eleetron temperature and eleelronconcentration, with the exac{ relationshipbeing controlled by various coolingmechanisms, including Coulomb exehange,and the excitation of the fine·struetureenergy levels of oxygen and the vibrationalsIates of nitrogen.

By rnodelling the full energy baIance of thethennal eleelrons, including 16 differentcooling lenns and the effects of heatconduction, the value of Te under quietconditions can be predicled from theobserved values of eleetron coneentrationand 10.7 cm solar flux.

[176 km]

86.12.03 2000-2200 UT4000.

30001I fj •

~ !E~ ~'"'" l

,N

, , .~ . " ~.. " . .. . - . " .~ 2000 ~ ~ .~;. ::~...

r• -. ,i,'" •

'" ] :"'" 'Ir : ••'~

.... _.. .,. .. ~'~'......t-.P

. ... ~..."'~'" ~

'~r~ ~"".,...;t~:. '" .......,,'" <1000 . "\." )

J.. : ." . ,...".

!_-r

j,O

______1

10 11 1210 11 12

LOGne [m"] [114 km]

Fig.19. Eleetron tempermures at ropside F.region altil/lJes compared with electrOIl deflSities alE·region (lejt panel) and lower F-region (right pallel) altitudcs,

2h

o

,

•

JAN ttAA MAY JUL SEP NOV

"

Fig.21. The occurrence probabilicy of largejield·aUglled upflow evenls (velociry >100 m S·l, or flux> 1Ol3 m-z S'l) in 3 years ofCP-1 dara (1985-1987), as a fUIlClioll o[(a)UT and (b) Momlt (Kearing, Winser,Lockwood, Mu/ligan and Doyle).

The largest probability of such an eventoccurs near 21 UT, around the time Troms~

passes through the Harang discontinuily.

Slm"llaneous "pllCN e~!s at 350 and 41)0 11m

,

The terrestriaI ionosphere is a major soureeof plasma (both heavy ions and protons) formany regions of the magnetosphere, andEISCAT has played a major role in studyingthe thennal ian upflows in the ionospherewhich are required to supply this plasma. AstatisticaI survey of data taken during CP-lexperiments has revea1ed that large upflows(and downflows) are a common feature onthe geomagnetic field line through Troms~.

Fig. 21(a) shows the percentage frequencyoccurrence of upflow 'events' as a function ofUT, where an event is defined as an upwardvelocity exceeding 100 ro S·I or an upwardflux greater than 1013 m'z S-l (Le. an order ofmagnitude greater than the classical polarwind flux of light ions at greater altitudes).

"•

Fig. 20. Comparison of predicred andobserved values of Te' for rhe heighr range260-325 km, during quiet periods on 15 days(Breen, Williams, and Davda).

A statistical study of height-integratedconductivities, derived from EISCAT CP-3data recorded between June 1984 andNovember 1987, has been undertaken. Thesolar-induced component of theseconductivities has been modelled as afunction of the solar zenith angle; it can beapproximated by a linear function of thecosine of the solar zenith angle. Thecomparison between the panicle­precipitation-induced eomponent of theeonductivities derived from EISCAT dataand the statistical eonduetivity models ofHardy el al. (1989), derived from DMSPsatellite electron preeipitation data, showgood agreement in the morning seetor, but adiscrepancy of about 30% in the eveningseetor, when EISCAT conduetivities exceedthose of the Hardy et al. modeis. Thisdiserepancy can be explained by ionprecipitation. whieh was not included in theHardy modeIs, whieh is at least qualitativelyintense enough in the evening seetor, intenns of flux and energy. to ionize theF-region (Senior, Lilensten. Fontaine).

1400 1900 2200 2600 3000

OBSERVED TEMPERATURE (Kl

JOO,

1600"wa,

" 1200aw••w-C "00w-wCwa• 1/,,00

10001000

The correlation between the predicted andobserved values of Te is over 90% and theagreement usually lies within the accuracy ofobservation (Fig. 20). However, at the onsetof magnetic activity following a long quietperiod, the predicled and observed values ofTe begin to diverge (Breen, Williams andDavda).

27

Flg. 21(h) sh\.\ws 111"'1 Sill h I;vcllls are ItludJ1110le !lkd}' tu O\..CUf iu will(~r (the sewudpcak in SUJl1Jllef in fal:\ ilJises I;;nli..ldy fromOlll;; Y<;;,1y Jislurbc;J pClHAI in July 1987).ThcSt: upfJows afe t:urrelalco with incr~ases

III 1:-regiun jUli telllpCIJIUlC, whidl are ortensel;;n in association wirh t:hanges in the fit::ld­perpemlicular convectiol1, as might occurduring the passage of a convection shearthrough the radar bc:am (Winser et al., 1989;Keating, Winser, Lockwood, Mulligan andDoyle).

A series of fi ve nights of measurements ofthe topside ionosphere with the VHF radar inJuly-August 1988 was used to study thevertical transport of O, <llld H+ ions, and theresulling exchange of ion species betweenIhe ionosphere and the magnetosphere. IIwas possible to deduce ion densities andcomposition, ion and e1cctron temperatures,and the line-of-sight (venical) drifl velocityor 0+, up fn at Jeast 1000 km height. II wastound, fur lhe pl;;riod studied, that H+cOllcentralions remaiII low even on quietdays. Whereas velticul 0+ drifts l:an bededuced Jirect!y from II\(.: radar dala, thiswas nol tht: I..ase f{lr f Il. silll.:e the ludal is nOLsufficit:ndy s~nsiti':/t: lu lh~ Ht dlifl vdocity.A Ilh~lhuJ \Vas (kvdlJlJed anu tested, inwlJid\ the coupletl mowelllUm equatiolls ofthe two ion Sptt:i~s and of the dCC(IOll gasar" sl)!vrd I~l dl'dllCl' Ihe field aligned'Jdu(;ily of I il flUlll Iii\;, h,di.llll;e ol aH furCl::sprc;.'}0nl. All tClluS lIt' the momentullle4ualions can be dcduct.:d flOm the observedvenic.:<s! vilri.lliw\ (Ir radar JcriveuP;U<llll<'tt'r:;, glVCII 01 l!!l'dd lit lll~ Jll'lll..l:tl.IIIHlhjlh,!t' .1:11..1 U~Jll~lllll jlt;llllt:JI~ies. Till;;u\t'.tbuJ tJ~td WitS ~hOV'lII to UI;; ldiabk,l!lougit SCll~lliv", hl lht' dlOicl' of Ot/OI tllli:;il./1 ia\..hll, ilW! [I' ~I .. I; ICSldl.'t iII guud:j~>\..lll!..:It! \\!lh pll" .. \ Hl b)d.HJJYllallli~:

Jlh'\!l-;, 1,1 j!llJ ,,1lglllJd plasllld fluw. lt11luvilkJ il :'l)':.lcllI..llil. CSlllllillc uf 0 1 alld l·!t"ultlow 1l1lx,cS at Ihe lUIJ uf thc ouscrvcdregioIl, shuwing thill [le vtlodties allO tlUKI;;Sart: general!)' Sigllific,IlJl!y smalltr thancxpl.:cted for Ihe pol..u winJ sitllalion. ThecUl1lputations f<J1' the H+ drift vdocily rely onan allnospheric IlHxlel (ClRA-86) in order tocompute the collision freljuencies. Themajor Htuu'al alomic cOIll.:entrations in themodel ~hOllld b~ calibrated in order tot:1illillli7(' l\1r n:thld ot:pclld~llt;e of thec:J!c:ulalioll:l, i~ tbc Ilelltr~ll oxygen andhydrogtn wllc:t:nlrations for the 0+ ionenergy equation and the H+ continuity

eljUatioH lcspet;tiveJy. For the first EISCATVHF obsavalions used. from the Ju1y­August 1988 campaign, an overall agreementwas found belween the derived atOInicoKygen concentration and the CIRA-86model; for atomic hydrogen, the derivedconcentrations are a factor 2 to 5 greater thanpredicted by the model, showing a cleartendency for the model to underestimate Hconcentrations at high latitudes (Wu Jian,Blanc, Alcayde, Fonlanari and Kofman).

NON·MAXWELLIAN PLASMAS

For ion drift vclocities larger than thethenna! velocity of the neurral atmosphere,the ion velocity distribution functionbecomes increasingly non-Maxwellian andthe shape of the incoherent scatter specrradeviates from that which is assumed forstandard analysis. Model ca1culalions havebeen perfonned to investigatc this effecL Asan example, Fig. 22 shows the ell'or in thedetermination of Te as a function of E rp' Arelaxation l:ollisioll model was used fur thecaklllations, whidl means that the elTOrs areprobably over-eslimaled, and the ratio of thecol1isioll frequtl1cy ro lhl: ian gyrofrequencywas 0.6 (Cooper and Kohl).

'1'11(' range of e1cclric ficlrl amplitudes wherethe assulIIption of a bi-Maxwellian iondislribution is gool1 cnough to providereliable measuremeuts of eleclront~lllpcralurt', density and iorl temperatureaLlis~HIOPY w~re a!so detennined, asfUllctiulIs of the ion population, and of thedirection of observation relati ve to theIllagnclic lidL! (Hubert and Lalhuillcre,1%9).

The dfc~t 011 the errors of the assumed ion~uJlJpositiun, iu a mixture of ions 0+ andNO~ was also studied. Decause the two ionspecies do not have the same anisotropy,their line-of-sight temperatures will differ atall aspect angles other than 54.T. Thisimplies that the errors of estimation oncomposition and temperature are not on lydue to the spectral distortion, but also to thefact that thc usual assumption of the sametemperature for both species is no longerV<lliu. Olle main conc1usion is that thevalidily domain of the standard analysis, as afunction of the parameter D" (the ratio of theiOH-neutral differential velocity and neutra!

thenna! velocity) and the aspect angle, issmaller for a nUxture of ions than for a singleian species. Secondly, the ian compositianis not weIl estimated, for measurementsalang the magnetic field line, when D· isgreater than 0.5. eorresponding to an electricfield amplitude greater than 20 mV m-I(Lathuillere and Huben, 1989).

1200

nificantly from the Maxwellian form; as theaspect angle decreases, the central peakbecomes less pronounced. By inc1udingmixed ion composition, a significantimprovement was found in fiuing some ofthe observed spectra. It was suggested thatNz+ fonned a significant proportion of themolecular ions during these observations.The influence of anisotropic ion velocitydistributions on ionospheric ion outnows tothe magnetosphere has also been studied.Such distribution functions produce anadditional upward force on the F-regionplasma. The magnitude of the upforcewithin a now burst event was found to befully consistent with the expectedionospheric signature of a flux transferevent. In one event, the hydrodynamiemirror force became as large as 10% of thegravitational downforce on 0+ ions at450 km altitude (Winser et al., 1989,Lockwood el al., 1989 and Suvanto et al.,1989).

'00

Te. K

'..... ~ "" ' . ,

6= 150·

,', 850

f-------~~

, .O 204060:80

E.L mV m-t

Te. K r

20 40 60 80

E.L mV m-'

of--~-<c:~'i:~, 700

"': 850. 1200

25

50 %

-50O

-25

HIGH LATITUDE CONVECTION ANDMAGNETOSPHERIC RESPONSES

Fig.22. Pereentage departure of estimatedMaxwellian eleetron temperature (T~)Ma:c

from T, (model) with E",p and T, (model) asparameters. The aspect angle of the radarbeam relalive to the magnetic field wasassumed to be 54.7·. a is the angle betweenthe Hall direction and~, to the radarbeam; 5, is zero when tlie team is in theplane defined by the Hall direetion and Il.

Observations of non-thermal plasmas atdifferent aspeet angles were considered andspectra found with well-defined centralpeaks. eonsistent with ion velocitydistribution functions which depan sig-

~---t---;-- D'O :2

-50020406080

E.L mV m-t

EISCAT CP~ l electron density profiles havebeen compared with simultaneous solar windparameters (B. V). It was shown thatdifferent heights in the ionosphere responddifferently to solar wind changes. At highaltitudes (>250 km) N, and the solar windparameter, V x B, were anticorrelated,probably due to enhanced recombinationduring disturbed conditions. At 10w altitudes« l00 km) the eorrelation between Ne andV x B was positive; this can be explained byprecipitatian of high energy particlestriggered by solar wind changes which causeadensity enhancement in the 10werionosphcre. lo the imermediate regime(lOO<h<250 km) no c1ear correlation wasfound, since the ionisation is controlled hereby several processes such as chemicalreactions. solar UV and convection whichdepend differently, or not at all, on the solarwind (Shirochkov and Schlegel),

The preclpuation of magnetosphericelectrons acts as a secondary source, inaddition to solar illumination, of ionizationand hearing for ionospheric electrons. Theintensity of these effeets eould be directlyevaluated from simuitaneous observations.approximately along the same magnetic fieldline, of precipitation fiuxes at the tap of the

, 1200

Te. K

o 20 40 60 80

E.L mV m-t

f--o-,07-~-'" '00"';:·-'.850

" - ~

1200

Te, K

'00., 850

O f-~~--.-'-<'.....~';~ --' ',:

50 %

25

-25

29

ionosphere (by VIKING) and verticalprofiles of ionospheric parameters (byEISCAT). Ionizatioll production in activeauroral fonns and lemperature profilesobserved by EISCAT, compared 'otheoretical camputations of the heating ratepruduced at each altitude by the precipitatingfluxes observed by VIKING, have beenconsidered. (Opgenoorth et al., 1989;Lilensten, Fontaine, Kofl1lan, Lathuill~re,

Eliasson and Oran).

possible link between two elear FTEs, seenwhen ISEE-2 was in the magnetosheath, anda flow enhancement and optical are whiehwere observed a few minutes later. The thirdevent may be associated with the 'BL spikes'observed by ISEE-2, a predicled FTEsignarure when inside the reconnection layerof the magnetopause (Lockwood el al., 1989;Elphic, Lockwood, Cowley, Sandholt,Lybekk and Farmer).

....1. __ ••• ..!._~., ,, ,,,,

.." ....-; ...-.....-_.. -'.....,-:"~

, ,............-,--.: ,..-t":~"-"~'"

10 -

,5 ',', ;.

I / ...... ~' \r·q,[W-..!..'

I molO' 5~71"n'e'~nIS0-' I '!lehn~abYO$C.>

' , I I.~ III ,Tt

..L J. J.J...L..J J L.I.._Ll_I-LJ..J.-Lu ! I l I 1_nOIJO 0020 0840 0900 0920 0940 1000

1 '1 :r" ., 1WC

~

~ 72:§co

i 70

Sh0l1-lived plasma now·bursts have alsobeen obs~rved by ElSCAT in the eveningand midnight SeelQr, especially duringsubstonn aetivity. The most commonsignature is seen in the easlward eleco-ojetwhen a southward burst eoincides with anenhancement of the westward plasmavelocity. Typically lhese bursts last for

Fig. 23. [SEE observations of magnelicfields aJ the magnetopause, EJSCAT jlowdata, and westward-movillg SS?.7 nmauroral lransients observed at Ny-A/esund,Spitzbergen.

oaf- 40~ 40

of 0--- - '--~--'1-""""""""-~'

~ : ,-.,.~N~}~r~, ,O "

l74 ::< """,.: .:."_ k ., ......

ISEE 2 (9 l, 10,621 iR,IGSE l Dec 1986§ 80 .-"'-'0,'-",c:-...",,\"'-"~T""''ri;;;~::::=lo:i,40 :: J

O ~~--

tISt~AT ohservarions Hl conjullcLion withtelevision camaas and photometers onSpuzbergt lI, :l<1Vl; lel'(;,t!cl! LiralllaLie nowbursts in lhe dnysitle auroral oval, lasting uptu 15 minutes, associated with transientauroral displays. The correspondingvohages inlegrated across the radar field·of~

vieware ()f the onkr of 60 kV and perhapsas large as 80-100 kV in total. The transientauroras form on the equatorward edge of thepersistent cusp/eldt before moving inta thepolar cap and fading. TIlis motion into thepolar cap strongly suggests that thesetransients are associated with Flux TransferEvents (FTEs) at the dayside magnetopauseand are not signatures of dynamic pressurepulses in the magnetoshealh which shouldremain within or equatorward of the deftregion.

The association of transient auroras and nowbursts with Frus has been snengthened bytwo separate studies. The flfst showed that,for continuously southwards interplanetarymagnetic field (lMF), the events recurredwith a mean repetilian period of 8.3 +/.0.6 min - similar to the mean repetition rateof FfEs observed at the magnetopause underthe same eondilions. Isolated events whichoccurred when lh~ IMF was predominantlynorthward werc cotlsistent with each beingtrigger~d by CI shorl~lived soulhward swingof the IMF. In the second study, FTEs weredirectly observeu at lhe dayside magneto­pause by tht: JSEE-2 salellite when in eloseconjullctioll with rhe EISC'AT/oplical field ofview. In (wO cases, classic FTE signatureswere foliowcd by an op!icaUflow burst eventin the gmuncl-bascd data, Fig. 23. Howcnh;:Ulcelllt;llb .Be clt"arly sten in theVOhäg~S 4'",,, Ulld $EW (Ul.:I'OSS the Illl(th-southand C<lSI-'.\'t;st dilnellSioll~ (Jr the radar field·of-view), :-,ilnilar lo tltuf;e pltwiouslyreported. hur '_v\:ilker btl·~lllse thc radar fieldof vi(;w uld nOl C:\ICIlJ us far north towards!ile \ll'licai an.:' The dU!'IIl;o lines intlicate <t

j\J

about 3-7 minules, and are repealedquasi-periodic sequence (Fig. 24).

CP-2-D 1988 AUGUST 9/10 278 hm

in a plasma at elevated velocity through theneutral atmosphere. eausing substantiaifrietional heating at all heights above about140 km. The same eleenie fieJds generatewave turbulenee in the E-region and cause asharp rise in eleetron lemperature between100 and 120 km.

EISCAT measuremems alone are not able todefine the total horizontal extem of suchevents, bUI on several occasions the burstsare seen in successive positions of the CP-2cycle, showing that Ihey are correlated overat Jeast 130 km in lhe north-south dircclion(Fig.24). Similar bursts are observed by theSABRE (Sweden and Britain Radar Ex.per­irnent) coherent radar and these measure­ments confmn that the panem can ex.tendover several degrees of latitude and at least10- of longitude (Williams, Virdi, Cowleyand Lester).

I'

_~ J~ ....nf1~"

" .

'P •

, .0

LO

-1.0

i~ O.S

l O.O+-v,............'r""'''~'U-;-:-Alrll'~0.5 TY

,.: 0.5a 0.0."',......,........""'=!

-0.5

-1.0

LO

-1.0-

-, .0

\1"':' I'IC':.' I-~O .:~," .. ,.l:'" " ~•. ' ,._,

Fig. 24. Fjeld-perpendicular plasmavelociry in the nonh-sourh plane at 278 km,measl/red on 9-10 AI/glISr 1988 for the fal/rpositions of CP-2. The errors represemtypical vallles for the evening and midnigJuseClOrs. EqllalOrward bursts of plasmavelocity, mllch larger than these errors, areseen ar 1822, 1937, 2037 and 2153 UT.

To measure sueh rapidly varying plasmavelocities it is neeessary to make nistaticobservations with sufficient time-resolution.Confinnation of the validity of the velocitymeasuremenls is provided by simultaneousmeasurements of ian temperature in theupper E and F-regions, and elenrontemperature in lhe E~region. The suddenonset of large eleetrie fields drives the

Bursts correlated over sueh large areasprobabJy represem penurbations of thewhole convection panern. For those evenlSwhere simultaneous IMF measurements areavailable, lhere is strong evidence that twosources of now are involved. A southward­tuming of the IMF has a direcl effect on thenight-time conveetian pattem, with a time­lag of about 20 min, and an indirect effect,associated with rapid tail reconnection, afterabout an hour (Williams et al, 1989).

Dayside now bursls have been found toshow very large zonal now velocities. On 9February 1988 ex.ceptionally largeconvection velocities attaining values of5 km s'\ were observed, Fig. 25. The evemlasted less lhan one hour, between 1530 and1630 UT, and covered r between 70" and72" geographie latitude, or about 200 km.The duration of the evem implies il

longitudinal ex.tent of about 400 km.Electron and ion temperatures in this regiunshow increased values with re!:pecl to thesUIToundings. The IMF was southward frum1330 UT umit at least 1700 UT, and themeasured ian line spectra inc1ude c1ea!signatures of non·Max.wellian ian velocilYdistributions.

This evem might be relaled to quasi-sleauyreconnection; however, ilS location and thelarge southward component of the now donot fit any of the known medels efreconnection. It could also be a secondaryeffeet of an evenl taking plaee on the

, I

anlisunward pan of the dusk callvectian cell(La HOl and Buchert).

""

~- ".. .-.... I

L"T,-~":C;-~~6- '-- -0---" -'~6

Hf'lt lUll

Fig. 25. Large vdocilies mctJsured byEISCAT 011 8 February 1988.

011 1; January 1989, even Iilghcr How.speeds appeared to peak at 6 km S-I, tllOUghthese measurements must be o·ealed withcaution as they were produced using Il

beamswinging technique. However. rhe iontemperatures. (estimated with allowaol:e fOf

lIon-Maxwellian distortion of the velocitydistribution) had peak values of about20,000 K, consistent with the flow ~peeds

and a simplified form of the iOIl energybalance equatioll. At the same time, atransient depletion of the plasma densitieswas observed, In all range gates, theenhancemelll of ian temperature and theplasma deplelion were observed at thewestern azimuth first. indicating thaI theevent propagated eastwards over the radarfield of view, The central region of eastwardflow was about 250 km in north-southeXlenl. with an associated potential of 55 kV.

In the signature of an FTE, the mean plasmaflow velocity, averaged over the newly­opened flux tube. should be the same as thevelocity of the event as a whole. Testing thiscondition is complicaled by difficulties indefining the extent uf the flux tube but it hasbeen shown that the transicnt bursIs observed

32

by E1SCAT <HlU opfkal instruments call meetthis critGrioll. For au FTE interpretation, thedimensions of the events studied aretypically 100-200 km north-south and 1500­2000 km east-weSt. AlIowing for thiselongatioll, the now piluerns observed arewnsistent with FrE moclels. The mappingof field lines from magnetopause toionosphere is Ilncertain, but the large zonaldimensions of lillCh evcnts support recentIheories or I~TEs in Itrms of time-dependentreconnecrion ,I( <In elongaled X-line(Lo<.:kwood, '~owley, SallJholt and Lepping).

The uaY:.ll1c I,;kl'l <JUII,lit i$ thought tO map totht k)w-l,'(lllllk hOlllld:lI)' layer (LLBL) ofthe lTIilgne!osl'licre. POLA observations. inClHljlll1cllon with optit:4d ubservations onSpitzhergGfl, h,lve rtveillcd flow signaturesaround p'lIdleS of uuroral luminosity at 14MLT, <.;e'~llllngly in the deft region, Fig. 26:-.h(lw'~ Ill'\'! welors (\{;ri\'cu by EISCAT,tiUJ>elllllp\,.;cd I' l lh..; 100lr~ ~e(;ond images of:iul,;ll il p,Jh.lI, 01..';1,;1 vnl by il (,10 nm CCD a1l­sky LalIILt:l ,Il Ny AlcSlllli\, As the patch(lJ ihs ca:-.lwald (tiJllwilnl). ellhanced flowsan~ uhst:'.... e<! whidl ;\fe IniLially westwardand Ihcll swil1g tilStWill"d. Althuugh eITors<lH llllllll..!ucl:d h,' Lht assumptions inherentiiI IhL; bc;'lIliswlIlt,;ing l\~l'llllique the observed~lIhilllt.C:lln::l1ts \Jf illll tCflIperacure aregCIl~ndly Lonsi:-.lcnl wllh thL:: uelived flows.

Ilg. 2K :.;II\IW:i il Sll1lti,11 t:\lt:ld near magnetic/11'0\111, /\;,',alll llll; JlO::liwd llows conlainc;ITor:-., Il,lfliclIlarly il! tlic highest laritudeswhere rhl~ beillll StPill<lliotl is very large, butlll~ vt:llx:ily of Ihe 557.7 /llll auroral fomls,dc:i.luL:ed l"rom lhe all·sky TV camera, is verydose lo the k>l:ill plasma now, as measuredby l~JS(,AT. l'llftht:r justification comesfrum th~ i(1I1 tetllpt::r,I\U1Ö estim:lted from theiOIl now vcClors; wtlh iJ number ofSilllplifying asswnpliolis, thc:se campare weilwith Iht 1l:ll1pCI<IIIlICS aClually observed byth~ rad~lr. Jmportant differences can befOllmJ, hut tlu:: ion relllpt'f.llurcs verify thl'major r~~ltUf\,.'s of the t:VClll ilS ueuuced fromthc bCilllISWjt,~illg. 1l:c!tlliqlJc. The patches of6:10 JIll1 aurora ure tholJ~hl to be related toblob-; of cllh:lrlced maglll:tosheath-IikeplaSlll.1 whiLh have hu..'n ohscrvcd in theluw htiludc 1l;:lunl'!,ll"v laytr (LLBl.); thenll\\' :-'1).:.1l~l!1l1 11','\' Idp "'.!jlldil.:ale betwcenscvc:ral ,hUll .J ill'p,datillg Ihe LLBL.tSanJhl,lt lod \'lOod, I,ybckk :l!ll..l farmer.I.liLtwlt,,,,I, SUIlJiIOll, 1";;lIlll,-r, Cowley,Lybchk lllld th\'d.ll

11 ( (HUU

t

2u l neJ .

o

. 30.00

1 km 5'Fig. 26. Seql«!nce of ]-second images/rom lhe630 nm CCD alf-sky camera at Ny-Ä/esund,Spilzbergen. An eosterly palch of 630 ron/umifWsiry can be seen af /4 MLT. Simulul1leousflow vectors from E/SCAT are also sllOwn. Thesolid line indicales the magnetic meridian afNy-Alesund. 1'r.e colour scale shows relativeintensity Wilh while a,i the weakest and blue asthe srrOllgest emission. (Sandholt. Loclcwood,Lybekk. and FW'lmr).

UT 23'"' OE(

Fig. 27. Average ionospheric paramelers from E/SCATCommon Progranu,~ dala observed atong the Troms# fieldfine over the heighl range 300-350 km al sImspol maximum(January 1988 ~ August 1989). The average eleclroncOllcentration. N,. declrOIl tempera/ure. T,. and ionlemperature, Tj• are shown as fUllclions of UT and lTUJnlh.The colour scafes run from blue 10 yeffow and correspond toarange of900-J600 K/or Tj (lower panel), 14()()-2600 K/orT, (middfe) and 0-1000 109m'] for N, (upper paMI).(Farmer, Fuller-Rowell and Quegan)

E:J:pcriIn."'l : SP-UX-POLl:l

n.mC !Dtcz-ql : 08:50:00 Q J-.nuary IQ6Q - Og,20:00 g J-.nU&1'7 111611

7<

72

0915

•--- -- -~

~

.:9 72..ro>, ~

$ ...... 70 -'------,----_,-----,-----.------,------'-70

<Il

'"'",.tllJ "16

'"el~

-- -

76

0855 0900 0905 0910

Universal TimeDIH5

._. _boundory of 630nm ouroro • - - ..peo\( ,nlen5,Iy 557 7nmouroro _peol( 'rllen$lly 557 7nm oCI,ve ourorol forms

Fig. 28. Transiemjlowlauroral evem observed near noon by EJSCAT and optical instruments atNY-Ålesund, Spitzbergen. The observed broadening and intensificatiofl of the band of 630 nmaurora and the transient active 557.7 /ini auroralforms in the cusplciejt region are accompaniedby transienc swings to weseward and then easeward plasma flow (Lockwood, COlVley, Sandholtand Leppillg).

'me response of the evening sector auroraloval ionosphere to a geomagnetic suddencommencement has been studied with theCP~l data. Immediately following themagnetic impulse, EISCAT observed asimilar impulse in the poleward electric fieldand in the F.region ion temperature (Fig.29). During the hour following the impulse,a strong depletion of the, still sun-lit,F-region developed, along with furtherincreases in electric field and iontemp~rature. lonosondes further southdetecled lhe equatorward progression of thedepletioll. These observations wereconsistem with an equatorward expansion ofthe high latitude convection patternfollowing the magnetic impulse, the depleteddensities beillg brought into the radar field ofview by w~stward convection of low densitynightside plasma (Collis and Häggström).

More quantilative investigation of theinereases of ion temperature at 279 kmaititude, and of the electric field, during the.

development of the density depletion showedthat the derived ion temperature did notinerease as mueh as would be expected if theian-neutral energy batanee were maintained.lr was suggested that the low iontemperatures were an artefaet of theassumption of a wrong model for ioncomposilion in the data analysis.

A second analysis, in which the iontemperatures were fixed to the valuesexpected from energy balance consider­ations, allowed the changes in ian compos·ition to be detemlined during the depletiol1.Significant increases in elecrron temperaturewere predicled by the seeond analysis and adepletion of Ot content to only 10% wasobserved in one example, Fig. 30(Häggström and Collis).

The efrects of magnetospherie eonvection onthe high-latitude atmosphere have beenincluded in the University College-Sheffieldthree~dimensional, eoupled ionosphere-

34

-.....,..-- .......---~._~-,-

Fig. 29. Detailed comparison of Ti, electricfield (both measured by E/SCAT at 279 km)and magnelic field variations al Kiruna on25 March /987. Gaps iII the EfieldmeasuremenlS are a resull of lhe scanningprogramme.

Electril.: fields and conduclivilies derivedfrom E1SCAT dala during the two GISMOScRmpaigns of JalllliU'y J9~4 ami September1986 w~r~ includt"'.d ll1 lhe NCAR data baseaou combined WIth observations from otherincoherent St;attcr raJufs, from HF radars,from ground·bascd magnetometers and fromsatellites. to mtlp tlte inslantaneous large­scale electric p(Jh:~lltial pattern in the auroraland polar regions, using the AMfE techniquedescribed by Richmond and Kamide (1988).

During pr.riods of hi!!h lH<lgnclic activity.cOlIvectiolI declri<.: fields C,IO pcnctratedirectly toWiUUS midJle dnd low latitudes.The electrical coupling between the high,middle and low-Iinilude ionospheres wasex.amincd usin~ dala frum f,ve incoherentscalter radars incJuJlng EJSCAT, lOgeIherwith inlerplanl::ol:try ~Hld bnlund~ba:.ed mag­netic data, for lhe GlSMOS period inJanuacy 1984. TIllS ddl.t set :-.hows lhat thetheorelil:al global convcCtiol1 medels repro­duce roughly thc main ,,;h:lfllcteristics of thcmit..lt..lle and low l<lliltllle electric fieldsassociated with the:: variatlf)r,s of lhe cross­polilJ-tap PUI\;lltl,ll Ull/p. l-h'WC\er, substan­tiai Jisagrtci lLl.:lll~ bt.:1 Wn'O ob'ie::rvations andmedels may appcilf, anu coull! be duc to thea,,;tion of thc uilllllfbunt.:o: U)%1I110 ~ffects 011middlr ,1IlLlI\)w l.llitwk ~kllri(' ficlds (Fcjer,Kcllt;y, ~il,11;1I1 ,Il: lO! 1 ,. 1I1j'uuil.'rt:, Hoh,Tepky. BlIrn$id~, 1\1Idl1. ;-)qhl:ll. Wtlodman,Knmidt: and t .cPPj{"~~.1

observed by Hit:. ~), 1I".lJ~:-'I!-JJl1 raU:JI, ,'l1dauroral alltl IJJidlallll!,I.. Ill.l~.ildHIlCIt:rt, wasa3sodatcu with ;I III I.It ~tall COllll actionObSl;;CVCtJ 1I\.,.!f uu..... k by EIS<..'Al' andsubstonn now sl.ln~c~,· ob~aved nearmidnighl hy SI~l1dreSlll'jjl, W~le i.lssocialcdwilh rapiu ~uurr,t(.·tIO!l pr Ilie I'0br cap l1eardawn, as ubst:rvtu by lilSCAT. FurtherstudIes hdve been l11ild...: with S~lndrestr~m

eilher id dawll l}f noorl wlnlt: ErSCAT waiiobs~rvillg in III\,; noo'l allO ,\.llcffloon seetorsrespectivt:ly Ob.\l;"rvatillm: dUflllg SoulhwlIrdturnings of the nu· (vb~,u v~J by the IMP·8satellite) shuw UHH the ol\:,cl \)1 cnhilm.:edconvet..:lioll I;t.:CUII\::d IUSI ill Ihe radilJ' closestto 110011, il:. prr..du.:tI:u IUl Iho.; model ofiOllosphetil: cOllvel.;lion J~civt:J from theEISCAT-AMIYfE dina on iOl1osphcricresponst". limes (Foster et al., 19S9; Clauer etallny; Lockwooo et al.. 19K9; Lockwoodand Freclnan, 19~~; Robinsull, R., Clauer,de la Ueaujanliere. Kt'lIy. friis-Christensenand Lockwood; IAJl:kwood).

._--.- ------'

~---~-----

B,B,

----------------,KIRUNA ~-

B,

15·~lO~~--,''',,-='-~-7.15''\O' ~ ,<>00

Time (UT)

~I

Auroral convectiol1 has been studied usingsimultaneously the Millstone Hill, EISCATand S~ndrestr~m incoherent scaUer radars.A series of convection 'snapshOls' madeduring an inten,al of increasing geomagneticactivity indicate that the large-scaleconvection pauem maintains a two-cellcharacter during substonn onset and thataverage medels derived from radar dataprov ide a reasonable representation of thelarge-scale convection pauern duringdynamically varying conditions. A substorm

thermosphere model, and the predictions ofthis model have been compared withaveraged ionospheric parameters fromEISCAT's Common Programmes (Fig. 27).Initial comparisons for medium to highlevels of solar activity showed goodagreement, with the numeIlcal model closelyreproducing the diurnal variations of the realdata in winter and summer (Fanner, Fuller­Rowell and Quegan).

35

. .... . . . .. . . . .... . . .

......;.

16

.: ...

« ............

0.9 >

" " ;.".; " ..

.. ::"""

.:. ;:: .

:>:' ....

"<; •.•...: ::: ", .

.;.;;: .. . .... " ... .. " .....

. .' "

15

;: ..;:.:<:

14Time (UT)

0.9

0.7

.... ....

....; .. :: .. , ' .....

: .. '.-........... ",'o •••• :::: •••

.;:-::' -, .;.',-.:--.:.

. .. .

40 O ---,.-,~~,...,..,~~~",.

: ::::::::::::,:.:. . =)}V<?{,'-. . . . . . . . . ",".:.'. , .':':' .

~ 350E~~

2:)0

Fig. 30. Concours o/ Qt/N. belweell 225 ami -100 km on 28 July /987 tu derived from thecomposirion-dependenr unalysis.

EISCAT oistatic ion velocities from CP~3

data obtained between June 1984 andNovember 1987 were used to construeiempirical statistical medels of convecliollelectric fields and electrostatic potential as afunclion of Kp. These models provid~

estimates of the total pmential drop in thefield of view of the radar (a lower estimateof the total cross-polar-cap potential) and ofils variation with Kp. They also show huwthe latitudinal and longitudinal extensions ufthe convecLion cells, the rolation of thcpotential pauem relative 10 the IlOCJll

midnight meridian and the penelratioJl of th~deeoie fields towards mid·lallLuJc;!o vOJ.)'

with geomagnetic aCLivilY. The COlllpltn!oollI~tween these modds and thuse ublauwdJrurn the MilIstone Hill and Chuictlu"-.a lad.ll,tala shows genelally guud agrccmtlll. 'Hull,.Ilglu differences due to the geugz .. plLH..!.,..;arions of the Ihree raums tS~tll\.'.

I'."rllaine, Catluul, Akayt1c, FOOlUlliUI).

iII il IIJulti-radar sludy of tbe m.llll I· lqpllll

llhllglr uuril1g Ill~ SllNt)IAL lIllel"',:! !'

September 1986, the lrOugh was trackedfrom ElSCAT, 10 S0ndreSlrpm and MillsloneIIi II The observations of the trough atEIS< ~AT and S~ndrestr~m were pre­dOlllirlalHly in the neon and post·noon locallime seeiors, when the trough is associatedwilh strong westward convection. AtMills(OIIl' Hill Ihis was also the ease in theI',e: lllidOlghl sector, but in the post·midnight~cCltll thl; tfOugh occurred equatorward ofIlJl' \l;,~iull of largest eastward flow. These,il:,t'1 ",mUllS suggest that the trough may

1!<JVl IltllclGlIt generation meehanisms at,hl!l-rr-ul Il",-alllll1~S, or thai, onee fonned inPI'· l",lM hUon SCl::tor, the trough tends to ca·!tJI-lIl" :1:-' il slructure with in the ionosphereil ·;,11;1, h,s(er, Wickwar and Gustafsson).

I' .\ " 't!, pla~lIlit Sl.ructures, manifesting as,I dc; 11"11 I1cnslLy cllhancements whieh

" "'ll OV'-r lalge diMances in the highI. dIll 1(' cia'J pular cap ionosphere, so eal1edjolt.I,,,', !r"vc been slUdieu with EISCAT.

'1 ullly c1~ltlun density, bur also ian andI, +>(,u 1~lllpl.;lJlllreS inside the blobs, have

II . 111.\.1'\1 simultaneously for the first

.,

P,,,,,

o '\00. f, . lftOb'

D ,no,]" 1100.­

D /1<)0- l.' :~O<l"".

,.".

• IIIMI' 1.' '100~

[J '100- l, I~OO'

~, r,J...I './11,/ ~~<I 1l~1

l ,111'

:' I.. , ' I'" ", 1'0 I

o' '.o/n 111' ft' \D- '-flOliJ \

,•• 'T_ I\ -0'1 \\ '\'910 /; ej

\ ,, 'ti

10 to 20 mV m· l , inducing an anisotropy ofthe pressure gradient and increasing the rateof ()+ recombination. All these physicalphenomenon were included in a softwarecode which simulates the eleetron density asa function of time in three dimensions. Thecalculations show that the depression is duemainly to a recombination process caused byan inerease of the eleetric field andeonsequently to an inerease of the effectivetemperature for 0+ loss (Taieb, 1989).

...j--~,-_--T'---~-~-~n ", .9 Il ~~ ~:

lo'·lv<J'

Fig.31. Life history of'blobs' obrainedfromconsecUlive E1SCAT CP·3 scans

time. While the ion temperatures show nopeculiarilies, the electron temperature isquite variable. A positive correlation of Tewith blob geographic latitude. and a negativecorrelation with blob altitude. were found.From consecutive CP~3 seans, 'life-histories'of blobs were derived (Fig. 31); 'heyoriginate at high latitudes and low alritudes.plObably due to particle precipitation, (Iowerleft comer, Fig. 31) and plOpagate towaldslower latitudes and greater altitudes (upperright, Fig. 31), The electron temperature inthe blob tends to decrease with time, beingc1early enhanced after the blob is created andfalling as il travels through the ionosphere(Chen and Schlegel).

In thiny CP-3 experiments, between 1982and 1987, similar characteristics of theelectron density and ion temperature (in thea1titude l1lnge 250 'o 350 km), as functionsof magnetie local time and invarianlmagnetic iatilude during 24 hours ofobservation, can be found in lwelve cases.The most imponant of these is a large earlymorning depression of Ne, with an inereasein T j at the same MLT and invariant latitude.The electron density profile, and its variationwith time, depends on the produetion of ion­eleelron pairs due to solar radiation, therecornbination of the ions and their transportdue to diffusion, neutral drag and the e1eetricfield. Orten the eleetric field is greater than

OTHER SCATTERING PHENOMENA

Gyro Line Observations

Eleetron gyro line observations were madewith the EISCAT UHF radar in the summerof 1989. The gyro line eeho is displaced by afrequency f = (2n)" il cos(6) from thenormal ian line spectrum (where n is theelectron gyro frequeney and e is the anglebetween the directions of the wave veetorand the magnetic field). At UHF the line isusually very broad and difficult to detect, butnumerieal simulations show that it might beobservable at altitudes of 100-120 km, whereboth the Landau and the collisional dampingare not critical. An experiment was there­fore performed to investigate this possibility,where the UHF antenna was pointed 45- eastof nonh at an elevation of 10-. This gives ebetween 83.5- and 82.5- for backscauer at100-120 km. Strong echoes were reeeivedfrom about 100 km altitude. Fig. 32 is anexample of the returned power in a 12.5 kHzwide band upshifted by ISO kHz with respectto the transmiuer frequency. Echoes wereonly seen in this band or the neighbouringband at 125 kHz (the calculated gyro lineoffset is 138 kHz). Ten examples of suchsignals were found altogether but none lastedfor more than 30 s. At the time, thegeomagnetic field was very disturbed andthere was a very high proton flux (PCA)accompanied by strong X-ray radiation.These eonditions must be responsible insame way for the sLrong excitationmechanism neeessary to overcome thedamping and explain how Lhe gyro line canbe excited to sueh a high levet.

37

Coheren! E·region echoes observed at UHF

Coherent echoes in the auroral E-region,from plasma instability produced irregular­ities. have been further investigated,particularly their fUle structure in space andtime.

The dislOrted ian velocity distributionassocialed with large ion drifts in the aurora!F~region drive ion~cyclotron waves ~ the ioncyclotron micro-instability. By taking intaaccount the Landau damping of these waves,by electrons, il has been shown that theinstabilily can be exited for all values ofT-ffe• where T- is the field paraBel iontemperature and Te the electron temperature.The existence of microstructure in thedistribution of electron concentration withina scauering volume can cause non~linear

effecls in the relationship between theirregularity drift velocity measured bycoherent radars and the electton driftvelocity measured by an incoherent scauerradar. A study has shown that, for largeelectric fields, the stronges l seanered signalscome from regions where the electronconcentration is above average and the

COHERENT AND INCOHERENTSCAlTER RADAR COMPARISONS

Rice distribution. with a Rice parameter a =3.7, indicating reflections from orderedstructures in the scauering volume (Bragg~

condilian) together with noise. The shape ofthe backseatter spectrum did not changewhen the integration time was reduced from5 s 10 WO ms (Schlegel, T. Turunen andMoorcroft).

890818, 1129 UTEISCAT UHF RADAR30 s INH:GRATION TIMEl:l :; ijl, 5°t=1~OI<.Hz

1 . r- -,----,4 6 B 10

~ll AliV!:. I'OWLR

---I

I4U

O

140

160

Fig. J2. Gyro lim' rt:wm mea~ur~d cm 18Augu:lt 198Y, with flle l::JSCAT UJ/F radarpainting 45· east of /lurth at Wl devativ!tatlg/e of 10", 8 is the aspecl ong/t! and f isthe ojJset!requency of the receiver filter.

L 120~

i: 100

'"wz 80

High resolution measurements showed thatthe echo struClures are highly variable. Thealtitude of the srrongesl backscauer isusually less than 110 km but the measuredwidth of the srructures, 6 km, is probably afunclion of the antenna beam width; the truethickness of the layers being somewhatsmaUer. Often an apparent downwanlmotion of slIch stmcllIres is observed but thisis l1lure likely to be motioll in range, sincethe obsavations are made at low elevaliotl.Thc OCl:urrence of single 'blobs' in a contourplot of height/range versus lime areillterpreted as sauctures convecting lhroughthe .lOtenna beam (Fig. 33).

l". 1!.!'j-l\l} ·.11_. ,

",

.\ ..,i,

I' • ''',., , I

\

....

"

High lirne resolution was oblained llsing asped'll currelatof program which rccordedIht: imliviLiuai n.;lurtl of each radar pulse.Tbc JisuibutiOll nI" the bal.kscattcrlllllpllllldtS W;IS l""ulld [(I hl: appHI."<.inliltely il

Fig. J3. Smu:tures iII rangefheight and timeof ~{/herellt bal:kscauer produced byE~regjorl plasma i"srabWties.

\~

eleetrie field below average, leading to anunderestimate in the drift velocity measuredby the coherent radars (Suvanto, 1989;Uspensky el al., 1989).

A theoretical study of VHF eoherentbaekscatter has also been undertaken insupport of the new Coherent Scauer(COSCAT) experiment. The calculationspcedict that eoherent echoes reeeived by theEISCAT UHF receivers from the remoteCOSCAT transmitter should have phasespeeds signiflcantly highe, (20-30%) thanthose deteeted by VHF radars sueh asSTARE and SABRE. The flest COSCATmeasurements have now been made andpreliminary analysis of the data indieatesthat the eoherent speetra reeeived are verysimilar to the type l spectra reeeived at VHF(T. Robinson and Honary).

IONOSPHERIC MODIFICATlON(HEATING)

EISCAT observations during high-poweredradio-wave modifieation of the ionosphere atTroms0 indieate large inereases in Teassociated with the Heater tum-on. Detailedanalys is of these data has revealed excitingnew evidence for a heater-induced thennalcavitation effeeI. The temperature datatypically indicaled a peak in /!.TIf, (therelative change in eleetron temperature) of40% in the vicinity of the heater refleetionheight, which was usually elose to 200 km.Above the peak, /!.TIf, falls offapproximately exponemially as the altitudeinereases, with ascale length of a few tenkilometres. Below the peak, /!.TIf, falls offmarc quickly. The EISCAT observationsalso indieated that the temperature changessaturate after about two minutes of heating.The ehange ill eIteLrOll concentration,6.NJN", lypically reaches a maximu~..of30% at a height elose to the lnIUal

interaction height and falls to zero 20 kmhigher. Below the maximum, .6.NJNe falls to5% and then rises to a second maximum, ofabou! 20%, 20 km be10w the initial heaterinteraction heighI. The trough in .6.NJNeeonstitutes strong evidenee for heater­induced eavitation (Robinson, 1989),

In an ionospherie HF-modificationexperiment for whieh the Heater wasope,ated at 4.04 MHz and modulaled 20 son, 40 s off, EISCAT observed wavespropagating paralieI lo B~ and chirped, asweIl as nonnal, plasma line observationswere perfonned. Heater-induced plasmalines were observed only in the 'fust ID sintegration interval, indicating a strongovershooI.

These lines are unusual in that multiplesimuitaneous lines were observed, normallyoriginating within one kilometre of theentiea! region but sometirnes from lowerheighlS, and that the frequency of the mostconstam line is offset some 250 kHz fromthe hearing frequeney, with the other linesoccurring at greater frequeney offsets. Thenatural, photo-electron enhaneed, plasmaline was not observed; however, thebackground plasma parameters weremeasured using ion line observations.Comparisons with chirped observations,performed al EISCAT in May 1986, indicatethat increased Landau damping may beresponsible for both the strong induced~line

overshoot and the lack of a distinct naturalline. lon line power profile observationsshow the existence of a topside enhaneed ionline at the entieal density corresponding tothe heater frequency. It is believed this isduc tO strong OfZ-mode coupling paraBel toBo and low values of foF2. Thesephenomena are illustrated in Figs. 34 and 35(Jsharn, Kofman, Hagfors, Nordling, Thide,La Hoz, Stubbe).

39

EISCAT [on Power Profiles

17 August 19869:29:10 UT

----~~ 8otlomside ~r---~=::===~Enhancement

----~Topside_-t----c:;;;;~->~_.> Enhoncement

16 August 198612 :53: 10 UT

30011="'''';:;;,--

1001=--

E~

~ 200coa:

105 104

Powe r (,2 corrected i log scale)

Ffg. 34. Power projiles o/ the incoherem scaller ion line measured during ionosphericmodijicatioll experimems at EISCAT. There is clear evidence of enhancemenr bOlh arlhe /owerrej1eclion levet: x = (00,100) = l, and in the topside F-region, where x is also llnity.

Range of enhanced ion lineEISCAT 17 August 1986

.,."

'"1514

" _:........... • t • • ' •". . -..~.,;..:...

Il 12 13UT (hours)

109

.".-:. J.:.~ ..-. .~.':' . - ......:.

o', •• '.,-;;:. • •...-.

2~O

270

250

~ 230 -

:J,

~ 210 -

190

l"JU

ISOS

fig.35. The heighls of the /ower and upper ion Line power enhancemetlt ploued as alt/ncriorl oftime/or the observations of /7 August 1986.

40

NEW DIGITAL SIGNAL PROCESSING DEVELOPMENTS

Il was srressed in the minutes of the autumn 1988 Science AdvisoryCommiuee (SAC) meeting. that advances in coding and signal processing areamong the most cost-effective ways to get more and better science out of theEISCAT operation, and that new developments in these areas should begiven high priority. In keeping with that policy, this year's technology repanconcentrates on two Digital Signal Processing (OSP) development projecls:lhe hardware decoder for alternating codes and the digital FFf processor.

Experiments based on alternating codes have already become commonplaceat EISCAT, but the limited result memory of the correlator has made ilalmost impossible to use 32 baud codes and experiments using 16 baud codeshave been forced to sacrifice time resolution in order to achieve a practicalnumber of gates. Also, decoding alternating code modulations in thecorrelator has been impossible because of the lack of a programmableaddlsubtract function in the accumulator. However, the throughput rate ofthe eonelators is sufficiently high to make it attractive to search for apractical way of adding this feature.

A detailed study of the correlator architecture showed that it would berelatively simple to add a hardware device to the multiplier input structure,which could manipulate the sign of an individual sample being used as onefactor in a panial product. There were also some 'spare' bits in themicroprogram word, which had been assigned to features which are neverused in normal operation, and these could be re-assigned to the control of theadded hardware. A decoder unit based on this concept has now beendesigned and constructed (Fig. 36). At the end of the year, is was undergoingtests in the Kiruna site correlator.

E:o<TERI tAL DATA BuS ">or< .... " ... " • .".,.,.

------,............ftH

I'"C>

•..s ",,,.

R~~ COrilR'l:.l€R

,.,.'-- I--,.

,,~

~ '"ft-. ..,... NlIllPUUllORClII'flRC'_ " .. _' .....'10...lOGIC

CCIt:If'_~ICl:t

". '-"". !l(CO~11lC _Furt:rIClrl

~J

"'!lH~SS CC".....IE~~,_o1!ll(RF.<>C€

,~~ ClllC~lTS ".0'<"""- C<~'..._

K',

"".

Fig.36. Block diagram o/ the E1SCAT altemaling code decoder.

41

42

Within the new device, tables of the sign sequences for the only 32 baudaltemating code known (at present) and same of the possible sixteen andeight bit codes are stored ln PROM (programmable read only memory). Onesample at a time is fetehed from the buffer memory and stored in a registerwhere its sign can be manipulated according to a control signal which is thebinary exc1usive OR of two sign sequences read from the PROM tabIes. The're-signed' sample is then multiplied with another sample fetched from thebuffer memory and the product accumulaled to the result memory. Whencomputed in this way, all partial sums al a certain lag bccome properlydecoded and can be summed on top of each other in the result memory,resuhing in a rangevgated output whose range extent is no longer restrictedby the amount of memory availabJe.

The practical limitation of this de~oding scheme is the time needed forcomputing the large nUllIber of cross products, many of which are actuallyrecomputed with different sign se4uences for each range gate to which theycontribute. NevCt1heless, very practical range coverage can be achievedbefore the COO1pulation lime begins to limit the experiment perfonnance. Asan example, a 32 baud code rcquires a computation time of 112 ilS per rangegate. In a dedicaled E-regiun e;lCpefiment, this code can be handled for same30 gates without having to sacrifice more than same 2% of the possibIe dutycyc1e. For a baud length of 10 Jls, this corresponds to a range coverage ofabolJt 45 km (cg 90 135 km), which encompasses the main region of highconductivity. Sh0l1er codes, or coarser spatial resolution, can be used toextenJ Lhe wr1ge L:overagc.

The deco<1iflg <1evices are small v they occupy only two, single height,EW'ocards which can be fined in unused space towards the rear of thecorrelators . and they can be programmed through the correlatormicropro~ranl worus for uny code length. Truncated code sets are a1so101erated through proper programming, and any mixture of coded and 000­coded modulations can b~ ha.ndled. For e;lCtremely poor signalvtovnoise (SIN)ratios, the nett gain in the rate of statistics is on the average two to four timescompared to that of the present CP-I/CP-2. When the decoders have beeninstalled at all three sites, alternating code modulations can be used nOl onlyfor the E-region but also for velocity estimalian from a measurement atcol1isionless altitudes, resulting in even more effective experiments. It islikely that the Scientific Advisory Committee (SAC) will be recommended toapprove modified Common Prograrnmes employing altemaLing codeschemes as soon as the hardware and software have been validated.

The altemating code decoder is a typical in-house product. However, thenew fully digital FFT (fast Fourier transfonn) processor is the result of anunprecedented collaboration between EISCAT, the Swedish Institute ofSpace Physics and the FFT chip manufacturer. The processor is a one boarddesign using a comrnercial chip-set to achieve perfonnance between ten andtwenty times better than the existing CCD spectrum analyser. h wasoriginally designed at the Kiruna site in 1988, but has now been fullyintegrated by an EISCAT engineer during a two month visit to the semi­conductor manufacturer's plant, where he enjoyed access to proprietarydevelopment lools and evaluation software.

The prototype FFf processor occupies a dual Eurocard and confonns to theVME bus stanuard. It can penorrn a 512 point complex FFf in just 104 ilS,which makes il a very powerful tool for plasma line studies and ionosphericmodification diagnoslics.

PUBLICATlONS

Publications (Journals, Books), 1989

Araki. T,. K. Schlege1 and H, LUhr.Geomagnetic cffeets of the Hall andPedersen current flowing in the auroralionosphere, J. Geophys. Res.,~. 185-199,1989,

8jl."1rnå, N., Derivation of ion-neutralcollision frequencies from a combined ionlire/plasma line incoherent scatterexperiment. J. Geophys, Res,.~, 3799­3804. 1989,

Brekke. A,. C,M, Hall and T,L, Hansen.Aurora! ionospheric conductances duringdisturbed conditions. Ann, Geophys,.I. 269­280. 1989,

Brekke. A,. CM, Hall and T.L, Hansen,EISCAT studies of the aurora! ionosphereconductances, Adv, Space Res,. 2. 35-38.1989,

Clauel'. CR,. J,D, Kelly. M, Lockwood.R.M. Robinson, J.M. Ruohoniemi,O. de la Beaujardiere and L. Hakkinen,JUDe 1987 GJSMOS experiment: preliminaryreport on high time-resolution, multi-radarmeasuremenlS. Adv, Space Res,. 2,29-33.1989,

Collis. P,N, and L Häggström. Highresolution measurements of the mainionospheric trough using EISCAT, Adv.Space Res,. 2. 45-48, 1989,

Eternadi, A,. S'w,H, Cowley andM. Lockwood, The effecI of rapid changes inionospheric flow on velocity vectarsdeduced from radar beam-swingingex.periments, J. almos. terr. Phys.,,ll, 125­138,1989,

Foster. j,C. T, Turunen. p, Pollari. H. Koh1and V.B. Wickwar, Multiradar mapping ofauroral convection, Adv. Space Res., 2, 19­27.1989,

Fredriksen, k. N, Bj~må and T.L. Hansen.First EISCAT two-radar plasma-lineexperiment, j, Geophys, Res,.~. 2727­2732. 1989,

Hall, C.M., Recent D-region researclJ usingincoherent seauer radar, Adv. Spaee Res., 2,163-172.1989,

Huben, D. and C. Lathuillere. Incohercnlscattering of radar waves in the auroralionosphere in the presence of high elcctricfield and measurement problems withEISCAT facilities, J. Geophys, Res,. 21,3653-3662.1989,

Huuskonen. A., High resolution obsel vaticJOsof the eollision frequency and tempcratureswith the EISCAT UHF radar, Planet. SpaceSci,.n.211-221.1989,

Kaila. K. and R. Rasinkangas, CO-01dinatedphotometer and ineoherent scatter radarmeasurements of pulsating arcs with hightime resolution. Planet. Space SeL. Il. 545·553. 1989,

Kaita. K., R. Rasinkangas. P. Pollari,R. Kuula, J. Kangas, T. Tunmen andT. Bösinger, High-resolution measurcmentsof pu1sating aurora by EISCAT. opticalinstruments and pu!sation magnetometers,Adv, Space Res,. 2, 53-56. 1989,

Kersley, L.. CD, RusselI and S,E, Plyse.Scintillations and EISCAT investigalions ofgradient-drift irregularities in the high­latitude ionosphere, 1. atmos. terr. Phys., .il,241-247.1989,

Kirkwood. S, and P,N, Collis.Gravity wave generation of simultalleousaureral sporadie E-layers and sudden neun'alsodium layeTs, J. atmos. teIT. Phys., n, 259·269.1989,

Kirkwood. S,. L, Eliasson. H,j, Opgenoorthand A, Pellinen-Wannberg. A study ofauroral electron acceleration using theE1SCAT radar and the Viking satellite. Adv,Space Res,. 2. 49-52,1989,

Knipp OJ., A.D. Richmolld, G. Crc.wley,O. de la Beaujardiere, E. Friis-Christensen.D.S. Evans, J.C. Foster, lW. McCrea. EJ.Rich and J.A. Waldock, Electrodynamicpallems for September 19,1984, j, Geophys,Res, 21. 16913-16924, 1989,

hullnall, W., The F and E-n:::gion studies byinl.:uherent scalter radar, Adv. Spl1ce Res., 2,7-11,1989.

Kofman, W., K. Schlegel, U.P. L~vhaug,M. Lockwood and KJ. Winser, Comment on"nIl: effect of strong velocity shears onincoherent seauer spectra: a newinterpretation of unusual high-latitudespeetra', Geophys. Res. Lell., 1.6, 337-338,1989.

Kustov, A., M. Uspensky, A. Huuskonen,1. Kangas and E. Nielsen, On the thresholdelectric field for l m irregularity appearance,J. Geophys. Res., lM, 12043-12048, 1989.

LaneheSler, B.S., H. Rishbeth, T. Nygren,L. Jalonen and T. Turunen, Wave activity,Fl-layer disturbance and a sporadie E layerover EISCAT, J. atmos. terr. Phys., iL 179­196,1989.

Lathuilh~re,C. and D. Hubert,1011 composition and ian temperature<J.Jlisotropy in periods of high eleetrie fieldsfrom ineoherellt seatter observations, Ann.Geophys., 1, 285-296, 1989.

Lchtinen, M., On optimization of ineoherentSI;atter lneasurementS, Adv. Space Res., 2,l}J-141,ln9.

l Il! bWllod, M, S.W.H. Cowley,{ l{. ('(auer. H. Todd, S.R. Crothet's andDM. Wlllis, lon nows and hearing at a"'tJIl ,\('liJtg plll'll cap bOIlJlJ.ary: GISMOS"ll-:~j I/,Jljons ilhli ..... illiJlg viscous-like11,11 \'J\·tJUI. OJllht; n:'hlks 01" the magut:wtail,\.Iv. Spa<e Res., 2,,39-44, 1989.

1.'h.:kwoOO, M. and M.P. Fn::emall, Recentillllospherie observations relating to solarwlnd-magnetosphere coupling, Phil. Trans.Roy. Sac., A, m, 93-105, 1989.

Lockwood, M., P.E. Sandholt andS.W.H. Cowley, Dayside auroral activity and1l1Omentum transfer from the solar wind,Geophys. Res. Lett., l2, 33-36,1989.

Lockwood. M., P.E. Sandholt,S.W.H. Cowley and T. Oguti, Interplanelarymagnetic field controi of dayside auroralactivity and the transfer of momentum acrossthe dayside magnetopause, Planet. SpaceSei.,:rI, 1347-1366, 1989.

44

Lockwood, M., K. Suvanto, KJ. Winser,S.w.H. Cowley and D,M. Willis, Ineoherentseatter radar observations of non·Maxwellianian velocity distributions in the auroralF-region, Adv. Spaee Res., 2,113-118,1989.

Moffen, RJ., GJ. Bailey, S. Quegan,Y. Rippeth, A.M. Samson and R. Sellek,Modelling the ionospheric andplasmaspheric plasmas, Phil. Trans. R. Soc.Lond.. A, m, 255-270,1989.

Natarf, L., A.W. Wemik, E.o. Wodnickaand K. Schlegel, Deteeting travelIingionospheric disturbances in incoherentseaUer data using the Maximum EntropyMethod, J. atmos. terr. Phys., n, 389-400,1989.

Nygren, T., Studies of sporadie E·layer usingthe EISCAT incoherent scatter radar,Adv. Spaee Res., 2" 73-81,1989.

Nygren, T., B.S. Lanchester, L. Jalonen andA. Huuskonen, A method for determiningion-neutral collision frequency using radarmeasurements of ion velocity in twodireetions, Planet. Space Sci., n, 493-502,1989.

Opgenoonh, HJ., BJ.I. Bromage,D. Fontaine, C. La Hoz, A. Huuskonen,H. Kohl, U.P. L0vhaug. G. Wannberg,G. Gustavsson, J.S. Murphree, G. Marklund,R. Lundin, T.A. Potemra. S. Kirkwood,E. Nielsen and J-E. Wahlund, Cwrdinatedobservations with EISCAT and the VIKING~atellite: The de~ay of a w(;stward traveIIingsurge, Ann. Geophys.,1, 479-500,1989.

Parish, H., TJ. FuIler·RoweII, D. Rees,T.S. Virdi and PJ.S. Williams, Numericalsimulations of the seasanal response of thethermosphere to propagating lides,Adv. Spaee Res., 2" 287-291, 1989.

Pollari, P., A. Huuskonen, E. Turullcn andT. Turunen, Range ambiguity effeets in aphase coded D·region incoherent seatterradar experiment, J. atmos. teIT. Phys.,ll,937-945,1989.

Quegan, S., The influence of conveetian onthe structure of the high-Iatitude ionosphere,Phil. Trans. Roy. Sac., A, m, 119-137,1989.

Rasinkangas. R., K. Kaila and T. Turunen,Comparison of the lower barder of auroradctcrmined by two optical emission ratiomodeis, Planel. Space Sci., n, 1117-1126,1989.

Robinson, T.R., The heating of the highlatitude ionosphere by high power radiowaves, Phys. Rev., m 179-209, 1989.

Schlegel, K. and D.R. Moorcrart, EISCATas a alstatic aurora! radar, J. Geophys. Res.,!M, 1430-1438, 1989.

Shen Chang-Shou, Luo Yi and K. Schlegel,The feature of the ionosphere in the aurora!zone and the magnetosphere·ionospherecoupling, ChineseJ. Space Sci., 2. 127-135,1989.

Shen Chang·Shou. Zi Min- Vun andK. Schlegel, A C<tS~ study of the ionosphericmorphology at high latitude, Acta Geophys.Sinica,ll,262-269, 1989.

Suvanto, K., lon cyclolron instability drivenby non·thermal F-region plasma,Planel. Space Sci., n, 1-4, 1989.

Suvanto, K., M. Lockwood antiTJ. Fuller·Rowtll, The 1Ilfluem;e ofanisotrupic F-region i{'11 velocilYt.1lsuibutions on iOllOSpllCriC ion OlltflowsiOlO the 1O<lgm::loSphl.'l'l:, J. Geophys. Res.,21, 1J47-1J18, 1<)~9.

SUVi"lII{t), K, M. Lodwooo, KJ Winser,A.P. Funner and lU.l lsromage, Analysis ofincoher<;ll[ scalter spe<:lnl from nOll·Maxwellian plasma, Adv. Space Res., 2.,103-106,1989.

Suvanto, K" M. Lockwood, KJ. Winser,A.D. Fanner and B.1.1. Bromage, Analysis ofincoherellt seauer radar data from non­thennal F-region plasma, 1. atmos. terr.Phys .• il. 483-495. 1989.

Taieb, c., Simulation of the plasma densityin the polar eap F-region with a conveetionfield obtained from EISCAT observations,Ann. Geophys .• l, 355·363, 1989.

TaylOl, MJ., A.P. van Eyken. H. Rishbeth,G. Will, N. Will and MA Clilverd,Simultaneous observations of noctilucentclouds and polar mesosphere summer

echoes. Planel. Space Sci., 31.,1013-1020,1989.

Uspensky, M.V., A.V. Kustov,P.1.S. Williams, A. Huuskonen, J. Kangasand E. Nielsen, Effect of unrcsolvedelecrrojet microstructure on measurementsof irregularity drift velocity in aurora! radarbackscaller, Adv. Space Res., 2. 119-122,1989.

Virdi, T.S. and P.l.S. Williams, Observationsof tidal mooes in the lower thennosphereusing EISCAT, Adv. Space Res .• 2. 83-86,1989.

Wahlund, J-E. and H.J. Opgenoonh,EISCAT observations of strong ion outflowsfrom the F-region ionosphere during auroralactivity: Preliminary results, Geophys. Res.Lell.,l!i,727-730, 1989.

Wahlund. J-E., HJ. Opgenoorth andP. Rothwell, Observations of thin auroralioniza6on layers by EISCAT in connectionwith pulsating aurora, 1. Geophys. Res.,~,223-233, 1989.

Williams, P.J.S., Observations ofulmospheric gravity waves with incoherentseatler radar, Adv, Spaee Res.,.2., 65-72,19M9.

Williams, P.l.S. and T.S. Virdi, EISCATobservations of tidal modes in the lowerthennusphere, J. atmos. teIT. Phys., n, 569­577, 1989.

Williams. PJ.S., T.S. Virdi andS.W.H. Cowley, Substorrn processes in thegeomagnetie tail and their effect in thenighrside aurora! zone ionosphere asobserved by EISCAT, Phil. Trans. Roy. Soo.•A. m, 173-193, 1989.

Williams, P.1.S., A.P. van Eyken, C. Halland 1. Röttger, Modulations in the PolarMesosphere Summer Echoes and associatedatmosphelic gravity waves observed byEISCAT, Geophys. Res. Lell.,l!i, 1437­1440,1989.

Winser, K.J., G.O.L. Jones, PJ.S. Williamsand M. Lockwood, Observations of largefield-aligned nows of thennal plasma in theauroral ionosphere, Adv. Space Res.,.2., 57­63, 1989.

45

WIriser, KJ., M. Lockwood, G.O.L. Jonesand K. Sllvanto, Observations of non~thermal plasmas at different aspect angles,J. Geophys. Res., 2.'1, 1439-1449, 1989.

Winser, K.l, M. Lockwood, G.O.L. Jonesalltl K. SU\/anto, Radar observations of non­thenna! plasmas at different aspect angles,Adv. Space Res., 2.,107-112,1989.

Publications (Theses, Proceedings,Reporis, elc), 1989

PhDTHESES

Lilensten, 1., Resolution de I'equalion detransport et application dans le plasmaionospherique, These de doctorat,Polytechnique de Grenoble, 1989.

McCrea, I.W., Radar observations of energydeposition and dissipation in the high~

latitude ionosphere, Ph.D. Thesis, Universityof Leieester, 1989.

Natarf, L., lneoherent seatter observations ofacoustic graviry waves in the auroral zone,Ph.D. Thesis, Polish Academy of Sciences,Warsaw, 1989.

Parish, HF., Modelling the response of thethemlOsphere to lower aunosphere tides,Ph.D. Thesis, University of London, 1989.

Suvanto, K., Non-Max.wellian ian velocitydistributions in the ionospheric F-region,Ph.D. Thesis, University of London, 1989.

V:t!linkoski, M., Erfor allalysis of incoherentS\·;IUc:r radar m~asurel\lelllS, f'h.D Thesis,University of Helsinl-..i, l~g9.

M.Se. Tf! ESES

L~jdlohn, B-T., FirsL gyro line observationswith the EISCAT VHF radar, Cand. seient.Thesis, University of TromsS!S, 1989.

Mercer, A. , Qunsi-periodie variations inauroral zone plasma velocities, M.Se Thesis,University of Wales, 1989.

Maen, 1., Conductivity studies in the auroralionosphere by EISCAT, Cand. scient.Thesis, University ofTroms~, 1989.

46

PROCEEDINGS and REPORTS

Brekke, A. and C. Hall, Quiet timeconductivities of the auroral ionosphere,AGARD Conf. Proc., ID, 24.1-24.17,Neuilly, 1989.

Figueroa, D. and H. Kohl, Ca1culation of thetemperature and velocity of the neutral gasusing CP-3 da,a, AGARD ConL Proc., ID,25.1-25.4, Neuilly, 1989.

Franke, SJ, C. La Hoz, J. Röttger andC.H. Liu, Frequency domain interferomerryof PMSE, Handbook for MAP, 2l!, 210-221,Ed. C.H. Uu and B. Edwards, 1989.

Glauhor, N. and R. Hernandez, Temperatureanisotropy of drifting ions in the auroralF-region, observed by EISCAT,Max-Planck·lnstitut fUr Aeronomie report,MPAE-W-l00-89-26,1989.

Hall, C.M., A. Brekke, U.P. L~vhaug andB.N. Mrehlum, Background electrodynamicsmeasored by E1SCAT during 'he NEEDcampaign, Proc. 9,h ESA/PAC symposium,ESA SP-22.1. 153-157, 1989.

Jones, G.O.L., KJ. Winser, J. Röuger,C. La Hoz and SJ. Franke, A statisticalreview of the EISCAT PMSE 1988 data,Handbook for MAP,2l!, 126-130,Ed. CH. Lio and B. Edwards, 1989.

La Hoz, e, J. Röttger, M.T. Rietveld,G. Wannberg and SJ. Franke, The status flndplanned developments of ElSCAT inmesosphere and D-region experiments,Handbook for MAP, 2.Il, 476-488,Ed. C.H. Liu and B. Edwards, 1989.

La Hoz, e, J. Röttger and SJ. Franke,Dynamic spectra of PMSE mea5ured byE1SCAT at 224 MHz, Handbook for MAP,2l!, 248-256, Ed. C.H. Uu and B. Edwards,1989.

La Hoz, C., J. Röttger and SJ. Franke,Spatial interferomerry measurements withthe EISCAT VHF radar, Handbook forMAP,2.Il, 185-19\, Ed. CH. Uu andB. Edwards, 1989.

L~vhaug, U.P., Ionosfreriske forstyrrelser­kritisk for GPS? Erfaringer fra EISCATsUHF radar, Proceedings of Geodesidagene1989, Stj~rda1en, \6-17 November 1989.

J 'h ( ".1, I \i . I' I{, l\ql,lllS01l M. L:~lr'rdllUI II hUl~:i, illll llt:aullg tVCllb ,)ilSClVtO hyIlJt.l~l:;CI\T lad.ll, ACi.\RD cOllr Proc.,HL 26.1-26.llJ. Neullly, 1~~~.

Maudsllagen, H·P. ano K. Schlegd,Alillospheric gravity waves in the auroralsource region of TIDs studied with theE1SCAT CP-2 data, AGARD Conf. Proc.,441. 28.1-28.14, Neuilly, 1989.

Rönger, J., Mean, tiLtal and Ouctuating windsin the middle ulmosphere and lowerthennosphere observed during MAP/WINEin northem Scandinavia, Handbook forMAP, n, 179-209, Ed. B. Edwards, 1989.

Röuger, l, The interpretation of MST radarechoes: the present knowledge of thescattering/reOection and the irregularitygeneration mechanism, Handbook for MAP,2li, 68-82, Ed. CH. Liu and B. Edwards,1989.

~oLlger, J., u·e J ilI11JIC ,lrlJ C. Hall, mSCATobservations Jnring MAC/SINE 1111.1MAC/EPSILON, 1l,"dhook for MAP,l.l,370-376, Ed. B. Edw,lods, 19RIf

IHHlger, J. and C. La l hJt, Fllle ~lid...:lU1C 01J Joppler spectra of PUlil r mesospheresummer cchoes (PMSE) nhst:1 ved wilh theEISCAT 7.24 MH/. nld,l' l-i.uldbook fOfMAi-'. :..3, l07-ll.1, Fil \ .Il Llu alldU. i~lh\':lrds, lY8')

HOll,'SI,J (',J,II!,,, .11'1",,1.1 .111.1I J' 1.111. (,I :l','II~ . '''\' "1'·I·pI·lllllg illlll\lIdi.,. ddl'l'tt.d h. In,"I, 1\ ~;(llllljl,'l I 'npll!t.:1

~'"'' Ij·l "I pl,lal IIICSlr'I,I'I:It" ~W'IIIIl;1 cdlu~':'ll·t,],.!, Ull"l ,,,,,-,j wull !ll~ E1~(.~AT

.' .'., I,ill/. I ,,1,1l. tluLK1\.uok fUl MAl",~.

'",' ~n. Ld C II l iu ;Iull 13. EdwanJs,jl)st)

HöLlgt:r, J., M.T. Rit:(vdd, C. La Hoz,T liaII, M.C. KeHy ami W. Swöctz, Polarllll::~ospheresummer t:choes observed withthe EISCAl' 933 MHz and CUPRI46.9 MHz radars. Handbook for MAP, 2l!,16~·178, Ed. C.H. Lill and B. Edwards,19~9.

Schlegel, K., Allroral bJckscatlercharacteristics (at 16 cm wavekngth andlarge aspect angles), Max-Planck-Institut rurAeronomie reporl, fvlPAE-W-05-89-24,1989.

Sl:hlt:gd, K. and D.R. Moorcroft, Unusualechoos obstrved with EISCAT, Max·Planck­lnstitut fUr Aeronomie repart,MPAE-W-05-89-13,1989.

Wannberg, G., l Rönger, C. La Hal andP.J.S. Williams, Long range planning fordevelopment of full MST capabilities atEISCAT, Handbook for MAP, 2li, 544-548,Ed. C.H. Liu and B. Edwards, 1989.

Wannberg, G., J. Rönger and T. Sturk, Gainand phase ca1ibration of the EISCATreceivers in MST applications, Handbook forMAP, 28., 549-555, Ed. C.H. Liu andB. Edwards, 1989.

Williams, P.J.S., A.P. van Eyken, C. Halland J, Röttger, Polar mesosphere summerechoes and associated atmospheric gravitywaves, Proc. 9[h ESA/PAC symposium,ESA SP-29 l. 187-191, 1989.

SUPPLEMENT 1987

Blallc, M , 1). Fontaine, R. Glowinski andL. Reitlllart, NUlllerit:al simulation of theIlldgJlttt/$i1J11t:ril; dttuun transportph~nlJlll~nd hy lillite dements and a methodIlr characteli::.tics, SeJies: 'AppliedMalheulutics', Gordon and Breach, SciencePublisltcls, (ne., USA, 1987.

VIDEO

Nltil d'Aur\)fc:;: I~s relations soleil-terre,n. Ah d)'de, M, Blam.:. n. Funtaine,U. Pcd\:f:.cn PI\)Itw..-cr: 1). Pedersen.French versiun: 1~88

Ellglish vt:fsil)ll: 198~

47

i'~ISCAT REPOlrrS AND MEETINGS

EISCAT Technical Note, 1989/49, Error Analysis of Lncoherent Scatter Radar Measurements,Vallinkoski, M., PhD Thesis, University of Helsinki, 1989.

EISCAT Tochnical NOle, 1989/50, Proceedings of lhe EISCAT Summer School, Troms~,Norway, August 1986, C. La Hoz and A. Brekke (Editers).

EISCAT Technical Nate, 1989/51, Non-Max;wellian lon Velocity Distribution in the IonosphericF-region, Suvanto, K., PhD Thesis, University of London, 1989.

PMSE87188, The Observations of Polar Mesosphere Summer Echoes with EISCAT in Summer1987 and 1988; Compilation of Reparts and Publicalions. J. Röuger (Ediwr), 1989.

Report presented to the EISCAT Council, 'An HF Heating Facility for EISCAT: The ScientificCase" EISCAT.Healing Working Group, Robinson, T.R. (Chairman), E. Mj~lhus, M.T. Rielveld,P. Stubbe and B. Thide, Ocrober 1989.

EISCAT Information Leaflet, A.P. van Eyken and J. Röttger (Edilers).

ElSCAT Annu.1 Repon 1988.

Meeting fepmts:

EISCAT Meelings No. 89/14, Proceedings of the EISCAT Annual Review Meeting 1989, Hetta,FIl1Ii1nd,27 February - 2 March 1989, G. Wannberg (Editor).

rl;lc~tings 1989:

( '( lUNCH,

48

3:~nl Jllel:tillg. ~-I O November

3()lh ml~~IiJ1g. 41unt:37lh Illl;r:!ing. J7-IS Octoher

L~\ltllllt;~lIl1g. " April1 Il J lur,ding, l~ Septelllber

DidcOl, UK

Sigtuna, SwedenKiruna, Sweden

Hamburg, Federal Republic of GennanyTromS!l1, Norway

BALANCE SHEE-::' f~'2:-.'. DE·=Er~1[B>ER !98~

MSEKAl

31 Dec1989

Al31 Dec1988

92.7 I 92.815.6 17.225.1 25.10.4 I 0.4 I

I i, 133.8 ! 135.5 I• 59.1 I 65.9 I

74.- 69.6

L,::' c.:C.~ 1.:~ .

4.-:I-.r

4 .. J ..

O.: ~ '(~ ..

O': 0.4i 2.9 I 3.1 I

3.1: 3.5 I82.1 I 80.9

Liabilities

CAPITALCOnlributions

:--:,.jl ta. :'''''I~:-''_

J.J.

PoolCapita! OperatingIn KindOthe~

iora. :a0I~

Deorec13uor. '

':;0:'::4 "'\.:'::.lWl_

-- ~-- -­.~._ ....

lO~ :'",abil1tJe~

:::)~ j .es"r-, ~

L~.Br:...:ili:

t70"iSlOIL:'Jme: :"iaoiliue.

GR.~ND TGT.A..:..

... _..,)

6<;••

MSEr'

~

6.0'1.6

O.:

7.'-

L:

<(J ..

0-'

J.Yl~Lo~.

Al Additions IDeore-; f._31 Dec ciaiion.: I 3, De:1988 Pool CapOp Other I , 1989 .

; ,J !

8.0 I C.2 I 7.b29.1 0.1 I I

U; I 27.4 i13.4 1.3 I 12.1l7.1 L5 I 15.6 :4.7 0.6

,I :.!

,Ci r

2.4 : LO I OC. i :.5, - - - - -- -! 74.7 ! O••

I. I

~

..~ .... -'.i-. c· ••

....:.z.. ~.:. J::a.:r~"

,.,..--:".",,:.,. . .

~.• ...! J: C:;:~~.::

..... ::..;.-, r.' .~~·u;

J~

- ....~ .-":~Jl;r.:

J~'\:"[' TOT.-L

Assets

FIXED ASSETSBuildingsTransmitlcrsUHF Antennasn-IF Antenna~omputers. etcOt.le-

1ma

Total budgel in 1989 (MSEK): Recurrent c!laoter: Personne:. Aammistratior.

Oi>ecanon~.

Töta!.CapiraJ Inycsunenl chapter:

MSEI:8.563.94~.21

16.712.60

ToraJs may nol match because of rounding, MSEK =Million Swedish Crowns

EISCAT SCIENTIFIC ASSOCIA.nON 1989

31 December 1989

COUNCIL

France

P. BauerA. BerroirG.Caudal

Finland

J. KangasA. Siivola

Federal Republicor German)'

W.I. AxfordG. Haerendel

G. Preiss

Norwa~'

O. HavnesB. Bemerud

Sweden

B. Huh.qvislM.O. Ottosson

United Kingdom

WJ.G. BeynonT.B. Jones'B.R. Martin

SAC

AFC

I•

II I

I ID. Fontaine

IT. Turunen W. Baumjohann

IN. Bj0må

IH. Opgenoorth

IS.W.H. Cowley

W. Kofman K. Rinnert PJ.S. Williams

I C. Blamom I I O. Ranta I I M. Meinecke· I I A. Andersen I I J. Gustavsson I I D. MorreU ISAC = Scientific Advisory Commiuee

EISCAT Senior Starf

DireclOr: J. RÖllger (on secondmem from MPG)Depuly Director: G. WannbergBusiness Manager. P. Hagström

AFC = Adminisll"ative and Finance Commillce

Senior Scientist A.P. van EykenHead of Compuwr Operations: S. Buchert

• =Chairman

Sile Leaders: Kiruna: L WolfSodankylä: M. PostilaTromS0: R. Jacobsen

THE EISCAT ASSOCIATES

CNRSCentre National de la Recherche Scientifique

France

SASuomen Akatemia

Finland

MPGMax-Planck-Gesellschaft

Federal Republic of Germany

NAVFNorges Almenvitenskapelige Forskningsråd

Norway

NFRNaturvetenskapliga Forskningsrådet

Sweden

SERCScience and Engineering Research Council

United Kingdom