g. marklund space & plasma physics, school of electrical engineering, kth stockholm, cluster...
Post on 14-Dec-2015
214 Views
Preview:
TRANSCRIPT
G. Marklund
Space & Plasma Physics, School of Electrical Engineering, KTH
Stockholm,
Cluster multi-probing of the aurora above and within the acceleration region
goran.marklund@ee.kth.se www.spp.ee.kth.se
C2
C4
C1
C3eastern bulge
middle surge
EFW meeting, IRF-U, 24-25 Aug 2011
Göran Marklund S. Sadeghi, J. Cumnock, T. Karlsson, P.-A. Lindqvist, Space & Plasma Physics, KTH, Sweden
H. Nilsson, Swedish Institute of Space Physics, Sweden
J. Pickett, Dept of Physics and Astronomy, U. of Iowa, USA
A. Masson, ESA/ ESTEC, NL
C. Forsyth, A. Fazakerley, MSSL, University College, UK
E. A. Lucek, Imperial College, London, UK.
Y. Zhang, Johns Hopkins University, APL, USA
Cluster AAR study team
EVENT aurora distrib geomagnetic activity Objectives, status
Event 1.29 May 200912:15-12:35 UT
S hemisphere
Mapping of surge and bulge using Cluster data from different MLT crossings meridional & lat current closure
On-going study, Sadeghi et al. 2011
Event 2.31 May 200921:05-21:35 UT
S hemisphere
Electrodynamic coupling of surge head arc and horn arc, origin of deep density cavity in between
On-going study, Marklund et al. 2011
Event 3.5 June 200915:30-16:00 UT
S hemisphere
Electrodynamics of double arc system, interaction between Alfvénic and qs acceleration in PCB and R1 of upward currents
in print JGR, Marklund et al, 2011
Event 4.5 June 200916:50-17:15 UT
N hemisphere Phys. Rev. Lett, Marklund et al 2011
DMSP F16
Cluster
On-going AAR studies and recent publications
F16
First 2-D mappingof AAR of large-scale auroral arc
C2
C4
C1
C3
eastern bulge
middle surge
EVENT I 29 May 200912:15-12:35 UTS hemisphere
Orbit & auroral geometry
Approach 1.
The Bvectors indicate local FAC sheet orientations. which may be related F16 auroral sheet orientations This is one way to infer the bulge motion between the times of the Cluster crossings and the image time
Geomagnetic conditions
Bvectors along Cluster orbits
1 hr MLT
C1 Central Bulge
12:33 UT
12:17 UT
The widths match for a W-ward displace-ment of the C1 trajectory by 1 hr of MLT
The bulge moved 1 hr of MLT in 16 minimplying a W-ward speed of 0.7 km/s
Approach 2To estimate the width of the upward FAC region from Cluster data, scale it to the Ionosphere, and find the location where this width matches that of DMSP aurora
C3 Eastern Bulge
C3
C3 lagged behind C1 by 9 min. The C3 crossing took place 7 min prior to 12:33 UT, implying a W-ward reldisplacement of 0.4 MLT of the C3 trajectory
12:15 12:20 12:25 12:30 12:35 UT75.6 74.5 73.1 71.3 69.1 ILAT23.4 23 22.7 22.4 22 MLT3.62 3.44 3.27 3.09 2.92 RE
21:33 UT
C2
C1
C4/C3
EVENT II 31 May 200921:05-21:35 UTS hemisphere
Orbit and auroral geometry
Geomagnetic conditions
EFW and FGM data overview
R1 R24 kV
0.5 kV
Horn
electric field
magnetic field
FAC
electric potential
-s/c potential
Up-going electrons
down-goingelectrons
R1 R26 kV 4 kV
0.8 keV1 keV
4 keV6 keV
Surge Horn
Up-going electrons
down-goingelectrons
up-goingions
electric field
magnetic field
FAC
electric potential
-s/c potential
C1 C2Surge Horn Horn
plasma density
ADCplasma density
ADC
ADC
plasma density
plasma density
R1 R2
1 keV
7 keV
8 kV 6 kV
Surge Horn
electric field
magnetic field
FAC
electric potential
-s/c potential
Up-going electrons
down-goingelectrons
up-goingions
1 keV
6 kV 4 kV
4 keV
R1 R2
Surge Horn
electric field
magnetic field
FAC
electric potential
-s/c potential
Up-going electrons
down-goingelectrons
up-goingions
up-goingions
C4 C3Surge Surge Horn Horn
ADCplasma density ADC
plasma density
Horn arc Surge Head, Horn Surge Head, Horn
Horn
C2
C1
C4/C3
Horn C2
C1C4/C3
C2 C1C3
C4
Surgehead
Surgehead
21:22
21:20
21:15
EVENT II SUMMARY 31 May 2009 S oval 21:05-21:35 UT
orbit overview
weakly merged strongly merged arc potentials arc potentials
DMSP F16 data
18
C4, C3 15:36 C1
BU
LGE
21
70
80
HO
RN
Cluster
Cluster EFW and FGM data
EVENT III 5 June 200915:30-16:00 UTS hemisphere
Orbit & auroral geometry
DMSP/F16
Geomagnetic conditions
Marklund et al., in print JGR 2011
EVENT III SUMMARY
Spatial & temporal evolution of AAR potential
• Coincides with jllup
• Depth varies ll
• neADC << 1 cm-3
• neamb ~ 1-2 cm-3
C1 C4 C3C1 C2 C3
Acceleration potential estimatesfrom electron, ion, & E-field data
Auroral density cavity
Marklund et al., JGR 2011, in print
2D acc potential of AAR of Inverted-V aurora
E
Ell
1.4 RE
1 RE
1 2
ll
3
EVENT IV SUMMARY5 June 2009, 16:55-17:15 UT
Orbit geometry
Geomagnetic activity
• Similar & width of down-going e- & up-going i+
• The acc potentialis stable on > 5 min • Total ll
T for structure 1 = 4 kV; and 2= 6-7 kV • Scale size of E<< (=) scale size of FAC at 1 (1.4) RE
C1C3
Phys. Rev. Lett. Marklund et al.,2011
top related