Possibility of prediction of solar proton events

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  • ISSN 1062-8738, Bulletin of the Russian Academy of Sciences: Physics, 2007, Vol. 71, No. 7, pp. 945947. Allerton Press, Inc., 2007.Original Russian Text V.M. Dvornikov, M.V. Kravtsova, A.A. Lukovnikova, V.E. Sdobnov, 2007, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2007,Vol. 71, No. 7, pp. 978980.

    945

    INTRODUCTIONPrediction of solar proton events (SPEs) meets sig-

    nificant difficulties due to a number of hindrances, themain of which is the absence of theoretically justifiedalgorithms for this problem. For this reason, it is impos-sible to determine necessary and sufficient signs forrecognition of a preflare situation on the Sun. However,even in if this problem were solved, there would be dif-ficulties with the prediction of localization of fluxes ofaccelerated particles in the interplanetary space, andtherefore, with the prediction of their arrival at theEarth. Apparently, the only situation allowing solutionof the SPE prediction problem is the case where theflare energy is accumulated due to the dynamics of thecurrent systems that are not only localized in the solarcorona but also extended into the heliosphere. In thiscase, it is expedient to try to detect SPE precursorsthrough diagnostics of the heliosphere from the effectsin cosmic rays (CRs), all the more that such diagnosticsis performed at the force lines of the interplanetarymagnetic field, which relate the Earth to the corre-sponding regions on the Suns surface at a given instant.Indications of the existence of such situations wereobtained in [13]. The purpose of this study is to imple-ment this possibility.

    DATA AND METHODFor analysis, we used the hour-average observation

    data on the proton intensity in the energy ranges 49, 915, 1540, 4080, 80165, and 165500 MeV, obtainedat the GOES-10 satellite [4] and the data on the inten-sity variations for CRs of different rigidity, obtained byspectrographic global survey [5] from ground-basedmeasurements at the world neutron monitor network(38 stations).

    In analysis, to describe the CR rigidity spectrum ina wide energy range, we used the analytical expression

    obtained on the assumption that the rigidity spectrum inthe Galaxy is described by a power function of the CRrigidity, and the CR intensity in the interplanetary spacechanges (due to the change in energy in regular electro-magnetic heliospheric fields) according to Liouvillestheorem, i.e., at a constant particle density along the tra-jectories in the phase space [6]. The spectral parameters

    1

    ,

    2

    ,

    ,

    , and

    R

    0

    reflect the following characteris-tics of the heliosphere: the parameter

    1

    characterizesthe changes in the CR energy due to the gradient andcentrifugal particle drifts in the helical interplanetarymagnetic field against the induced electric field and isproportional to the interplanetary magnetic fieldstrength, while the parameter

    2

    characterizes varia-tions in the CR energy in the fields of coronal massejections and is proportional to the field strength inthese ejections and to the solar wind speed. The param-eter

    =

    B

    /

    B

    0

    (

    B

    0

    and

    B

    are, respectively, the strengthsof the background and time-dependent interplanetarymagnetic fields) reflects the effect of time-dependentmagnetic fields on the CR spectrum (at a magnetic par-ticle rigidity

    R

    R

    0

    ), while the parameter

    =

    describes the effect of polarization electric fields

    E

    pl

    that arise upon propagation of accelerated particles inthe inhomogeneous field of the heliosphere. Theassumption about the existence of such fields is basedon Lindbergs laboratory experiments on study of themotion of a beam of accelerated plasma in a curvedmagnetic field (see [7] and references therein). In par-ticular, it was shown in [7] that, in a certain range of thebeam parameters, when a plasma is present in thecurved-field region, charges are separated due to thedrift of electrons and protons in opposite directions; apolarization electric field directed perpendicularly tothe magnetic field, depolarizing longitudinal currents,and longitudinal electric field (causing anomalousbeam deflection) are induced; the beam is transformed

    Epl2 /B2

    Possibility of Prediction of Solar Proton Events

    V. M. Dvornikov, M. V. Kravtsova, A. A. Lukovnikova, and V. E. Sdobnov

    Institute of SolarTerrestrial Physics, Siberian Branch of the Russian Academy of Sciences, Irkutsk, 664033 Russiae-mail: sdobnov@iszf.irk.ru; dvornikov@iszf.irk.ru

    Abstract

    The dynamic processes in the interplanetary space have been investigated on the basis of the timevariations in the parameters of the cosmic-ray rigidity spectrum. It is established that the change in the electro-magnetic characteristics of the heliosphere begins before the sporadic phenomena on the Sun. In particular, itis shown that the sporadic phenomena are preceded by generation of local polarization electric fields, a decreasein the magnetic field strength in small-scale heliospheric structures, and an increase in the potential differencebetween the pole and ecliptic plane. The use of these signs makes it possible to predict solar proton events witha lead time from several hours to several tens of hours with a high degree of confirmation.

    DOI:

    10.3103/S1062873807070155

  • 946

    BULLETIN OF THE RUSSIAN ACADEMY OF SCIENCES: PHYSICS

    Vol. 71

    No. 7

    2007

    DVORNIKOV et al.

    from cylindrical to planar; and the depolarizing cur-rents distort the initial magnetic field.

    It is reasonable to suggest that the energy exchangebetween accelerated particles and the background par-ticles of the solar wind plasma and CRs in the helio-sphere occurs via such fields, as a result of which therigidity spectrum of background CRs is transformed.This circumstance was taken into account in derivationof the analytical expression for the rigidity spectrumthat was used in the analysis.

    Thus, determining the parameters of the differentialCR rigidity spectrum according to the data of its mea-surements in a wide energy range during each observa-

    tion hour, one can monitor the electromagnetic charac-teristics of the heliosphere and their dynamics.

    The technique described above was used to monitorthe interplanetary space in October and November2003 and in 2004.

    RESULTS OF THE ANALYSISIn Fig. 1, the three top panels present (triangles) the

    observation data on the proton intensities in the energyranges 49 MeV (0.108 GV), 915 MeV (0.223 GV),and 5 GV and (solid lines) the results of the calculationsbased on the model spectrum and the obtained values ofits parameters. The fourth (from above) panel shows theDst index. The four bottom panels show the hour-aver-age rigidity-spectrum parameters

    1

    ,

    ,

    , and

    R

    0

    ,

    determined for the period under study.Comparison of the time variations in the parameters

    of the CR rigidity spectrum with the time intensity pro-files of low-energy CRs (the first two panels in Fig. 1)suggests that the electromagnetic characteristics of theheliosphere change on the eve of solar proton events. Inparticular, it can be seen that the following processesoccur several hours or several tens of hours beforeSPEs: local polarization electric fields are induced(increase in

    ), the magnetic fields in small-scale helio-spheric structures decrease (decrease in

    ), and thelarge-scale helical interplanetary magnetic fieldincreases (the parameter

    1

    ).This circumstance gives grounds to believe that

    SPEs can be predicted by monitoring the electromag-netic characteristics of the heliosphere (in real time) onthe basis of the effects in CRs.

    The set of these three signs was used to predict SPEson a two-month sample of data in OctoberNovember

    0.108

    GV

    10

    2

    10

    0

    10

    2

    10

    4

    0.223

    GV

    10

    2

    10

    0

    10

    2

    10

    4

    5

    GV

    10

    5

    8

    10

    6

    6

    10

    6

    4

    10

    6

    0200400

    3210

    1.20.80.4

    0.240.200.16

    0

    21

    5 1510 20 25 30 5 10 15 20 25 30

    October November

    2003

    1

    ,

    GeV

    R

    0

    ,

    GV

    Dst,

    nT

    protons (cm

    2

    s sr MV)

    1

    Fig. 1.

    Time profiles of the intensity of CRs with

    R

    = 0.108,0.223, and 5 GV (the results of the calculations and theobservation data are shown by solid lines and triangles,respectively); the Dst index; and the parameters

    R

    0

    ,

    1

    ,

    ,

    and

    of the CR rigidity spectrum for the period OctoberNovember 2003. The vertical lines in the top panel indicatethe instants of SPE predictors.

    protons (cm

    2

    s sr MV)

    1

    10

    2

    300

    Days of 2004

    200100

    10

    0

    10

    2

    10

    4

    Fig. 2.

    Time profile of CR intensity in the energy range 49 MeV in 2004. The dotted vertical lines indicate theinstants of SPE predictors.

  • BULLETIN OF THE RUSSIAN ACADEMY OF SCIENCES: PHYSICS

    Vol. 71

    No. 7

    2007

    POSSIBILITY OF PREDICTION OF SOLAR PROTON EVENTS 947

    2003 and a one-year sample of the data obtained in2004. In the top panel of Fig. 1, vertical lines indicatethe instants at which implementation of the noted signs(predictors for SPEs) begins. Figure 2 shows similarinformation for 2004, which demonstrates a high(about 90%) degree of confirmation for the developedprediction technique.

    CONCLUSIONSDiagnostics of the electromagnetic conditio