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