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G. Marklund Space & Plasma Physics , School of Electrical Engineering, KTH Stockholm,

Cluster multi-probing of the aurora above and within the acceleration region. G. Marklund Space & Plasma Physics , School of Electrical Engineering, KTH Stockholm,. middle surge. C2. C3. C4. eastern bulge. C1. EFW meeting, IRF-U, 24-25 Aug 2011.

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G. Marklund Space & Plasma Physics , School of Electrical Engineering, KTH Stockholm,

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  1. Cluster multi-probing of the aurora above and within the acceleration region G. Marklund Space & Plasma Physics, School of Electrical Engineering, KTH Stockholm, middle surge C2 C3 C4 eastern bulge C1 EFW meeting, IRF-U, 24-25 Aug 2011 goran.marklund@ee.kth.se www.spp.ee.kth.se

  2. Cluster AAR study team 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

  3. On-going AAR studies and recent publications DMSP F16 Cluster First 2-D mapping of AAR of large- scale auroral arc F16

  4. EVENT I 29 May 2009 12:15-12:35 UT S hemisphere Geomagnetic conditions 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 Orbit & auroral geometry B^vectors along Cluster orbits C2 middle surge C3 C4 C1 eastern bulge

  5. 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 C1 Central Bulge 1 hr MLT 12:17 UT 12:33 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

  6. 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 75.6 74.5 73.1 71.3 69.1 ILAT 23.4 23 22.7 22.4 22 MLT 3.62 3.44 3.27 3.09 2.92 RE

  7. EVENT II 31 May 2009 21:05-21:35 UT S hemisphere EFW and FGM data overview Geomagnetic conditions Orbit and auroral geometry C2 C4/C3 C1 21:33 UT

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

  9. Surge Surge Horn Horn C3 C4 Up-going electrons Up-going electrons down-going electrons down-going electrons 1 keV 1 keV up-going ions 7 keV 4 keV up-going ions up-going ions Surge Horn Surge Horn electric field magnetic field FAC electric potential -s/c potential electric field magnetic field FAC electric potential -s/c potential R1 R2 R2 R1 6 kV 4 kV 8 kV 6 kV ADC plasma density ADC plasma density

  10. EVENT II SUMMARY 31 May 2009 S oval 21:05-21:35 UT C2 Horn C4/C3 C1 C4 Surge head 21: 20 orbit overview C2 Horn C4/C3 C1 Surge head Horn arc Surge Head, Horn Surge Head, Horn C2 C1 C3 21: 15 21: 22 weakly merged strongly merged arc potentials arc potentials

  11. EVENT III 5 June 2009 15:30-16:00 UT S hemisphere Geomagnetic conditions DMSP F16 data Cluster EFW and FGM data Orbit & auroral geometry 18 DMSP/F16 HORN 80 70 BULGE Cluster C4, C3 15:36 C1 21 Marklund et al., in print JGR 2011

  12. EVENT III SUMMARY Spatial & temporal evolution of AAR potential Auroral density cavity Acceleration potential estimates from electron, ion, & E-field data • Coincides with jllup • Depth varies DFll • neADC << 1 cm-3 • neamb~ 1-2 cm-3 C1 C4 C3 C1 C2 C3 Marklund et al., JGR 2011, in print

  13. EVENT IV SUMMARY 5 June 2009, 16:55-17:15 UT Geomagnetic activity Orbit geometry 2D acc potential of AAR of Inverted-V aurora C1 C3 E^ 1 2 1.4 RE Ell DFll 1 RE 3 • Similar e & width of down-going e-& up-going i+ • The acc potentialis stable on > 5 min • Total DFllT for structure 1 = 4 kV; and 2= 6-7 kV • Scale size of E^<< (=) scale size of FAC at 1 (1.4) RE Phys. Rev. Lett. Marklund et al.,2011

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