G. Marklund Space & Plasma Physics, School of Electrical Engineering, KTH Stockholm, Cluster multi-probing of the aurora above and within the acceleration region C2 C4 C1 C3 eastern bulge middle surge EFW meeting, IRF-U, 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

EVENTaurora distribgeomagnetic activityObjectives, status Event May :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 Event May :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 Event 3. 5 June :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 :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 mapping of AAR of large- scale auroral arc

C2 C4 C1 C3 eastern bulge middle surge EVENT I 29 May :15-12:35 UT S hemisphere Orbit & auroral geometry Approach 1. The B  vectors 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 B  vectors 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 min implying a W-ward speed of 0.7 km/s Approach 2 To 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 rel displacement of 0.4 MLT of the C3 trajectory 12:15 12:20 12:25 12:30 12:35 UT ILAT MLT R E

21:33 UT C2 C1 C4/C3 EVENT II 31 May :05-21:35 UT S hemisphere Orbit and auroral geometry Geomagnetic conditions EFW and FGM data overview

R1 R2 4 kV 0.5 kV Horn electric field magnetic field FAC electric potential -s/c potential Up-going electrons down-going electrons R1 R2 6 kV 4 kV 0.8 keV 1 keV 4 keV 6 keV Surge Horn Up-going electrons down-going electrons up-going ions electric field magnetic field FAC electric potential -s/c potential C1 C2 Surge Horn Horn plasma density ADC plasma density ADC 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-going electrons up-going ions 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-going electrons up-going ions up-going ions C4 C3 Surge Horn Horn ADC plasma density ADC plasma density

Horn arc Surge Head, Horn Surge Head, Horn Horn C2 C1 C4/C3 Horn C2 C1 C4/C3 C2 C1 C3 C4 Surge head Surge head 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 BULGE HORN Cluster Cluster EFW and FGM data EVENT III 5 June :30-16:00 UT S 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 j ll up Depth varies   ll n e ADC << 1 cm -3 n e amb ~ 1-2 cm -3 C1 C4 C3 C1 C2 C3 Acceleration potential estimates from 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E E ll 1.4 R E 1 R E 1 2  ll 3 EVENT IV SUMMARY 5 June 2009, 16:55-17:15 UT Orbit geometry Geomagnetic activity Similar  & width of down-going e - & up-going i + The acc potential  is 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) R E C1 C3 Phys. Rev. Lett. Marklund et al.,2011