1. Recent KTH Cluster research
T. Karlsson, A. Collier, T. Johansson, S. Liléo (Figueiredo), G. Marklund, m. fl.

2. Pi2 pulsations within plasmasphere 2003-01-21
Andrew Collier, KTH and Univ. Of KwaZulu-Natal, Durban
Pi2 pulsations within plasmasphere
L = 4.6 MLT = 02:43 C4 m n

3. CONCLUSIONS C4 Poynting Flux, P m n
L = 4.6 MLT = 02:43 C4 m n P
CONCLUSIONS
1. Phase shift 90 between E and B, indicative of standing wave in radial direction – cavity resonance
2. Poynting vector indicates energy flow in azimuthal direction, possibly indicating open-ended cavity.

4. Cluster results j//up event 1 temporal / spatial evolution
of discrete auroral arcs
Figueiredo et al., AG, 2005
Temporal Evolution
Symmetric
U-shaped
potential
1keV
e- ↓
-10 V
(kV)
820 E
(mV/m) 3
j//
(mA/m2) O+
1-10
keV
10-38 ↑ ↓
↑O+ 0'
15'
30'
45'
V= ∫ E^ · ds
j//
s/c 1
s/c ’30’’
s/c ’30’’
s/c ’
35'
LS Inverted-V
LS Inv-V
arc
arc
V= ∫ E^ · ds
arc
merging together
intensifying
PSBL CPS
PSBL CPS PSBL CPS
Cluster s/c 1 obs
Upward 10 keV
O+-beam
GM050825

5. Cluster results j//up event 2 temp / spatial evolution
of discrete auroral arcs
DMSP image
DMSP
surge
surge horn
Cluster
South Pole ASI images
surge horn
poleward
expansion
0.5 km/s
Cluster s/c
Cluster observations
s/c 2 — +7’
s/c 4 — +22’
s/c 1 5 kV 10
mA/m2
20'
V= ∫ E^ · ds j//
surge horn
multiple arcs
merging
together
& intensifying
PC PS
PC PS
GM050825

6. Auroral current circuit
Evolution of pos & neg U-shaped potentials in two connected FAC branches
Marklund et al, 2006
s/c 1
s/c 2
s/c 3
s/c 4
acc ions
14 FEB EVENT SUMMARY
· bipolar, div E-field » 1.7 V/m
· PSBL / CPS boundary & Ne-grad
· scale size of 8 km
· DF^, increases from » 0.4 to 2.7 kV in 100 s
· DF// in jllup » - DF^ in jlldown
· Local Ne-min & E-region Ne-hole
· downward FAC » 10 µA/m2
DF// decreases
from 3 kV to 1 kV
acc electrons
conv E-field
DF^ = ∫ E^ · ds increases from
0.4 kV to 3 kV
s/c 1
s/c 3
s/c 2
s/c 4
div E-field
aurora
Ne-hole
black aurora
t = 0 s
t = 100 s
t = 200s
t=300s
Auroral current circuit
GM050825

7. evolution of div E-field structures
Cluster data
j//down event 2
evolution of div E-field structures
div E ^ Bt EN Bt EN
div E ^ = 0.3 V/m
-Vs/c V
-Vs/c V
EFW
FGM
data
PSBL CPS
up FAC
down FAC
PSBL CPS
up FAC
down FAC
div E ^= 1.7 V/m
div E ^ Bt EN Bt EN
-Vs/c V
-Vs/c V
PSBL CPS
up FAC
down FAC
PSBL CPS
up FAC
down FAC
Marklund et al, 2006
GM050825

8. 5. Evolution of U+-potential: Simulation of Event 1
Jll
ENS
equator
L= 8.25
L= 7.25
Cut along Cluster track
s. iono-
sphere
Jll
ENS
Cluster track
cross-section
Streltsov and Marklund, acc for JGR, 2006

9. Interpretation Bipolar
Where do monopolar and bipolar E-fields occur with respect to boundaries ?
Statistical study of bi- & monopolar E-field events
Johansson et al, accepted Ann. Geophys. 2006
Equatorward, monopolar E-fields, are found at the PC boundary in the evening LT sector
# mono- polar E
# bipolar E
increase
in β (%)
PC boundary 10
706 PS 1 16
253 PC
PSBL
CPS
Interpretation
(Marklund et al, 2004)
Bipolar E-fields are found at
particle boundaries within PS
Bipolar
Monopolar fields, if plasma,
dense enough to support
connecting FACs, exists on
one side of the boundary only
Bipolar fields, if plasma,
dense enough to support
connecting FACs, exists on both sides of the boundary
GM050825

10. beta ┴ potential Eeast Eequator bipolar monopolar
Johansson et al., accepted Ann. Geophysicae, 2006

11. Auroral potential and associated FAC reconfiguration
during thinning of the PSBL
Marklund et al, subm to JGR, 2006
t = t0
t = t min

12. Auroral potential reconfiguration: Cluster observations
Cluster s/c 1 t= t0
Cluster s/c 2 t = t min
PEACE
electron
data ^
PSBL
CPS
PSBL
CPS F^
EFW &
FGM data F^
Potential step
-Vs/c
-Vs/c
Potential well Es Es BT
monopolar
E-field BT
Bipolar E-field
FAC
FAC

13. Auroral scale sizes (ongoing)
5 km
5 km # #
S(n)
S(E)
Which are the characteristic scale sizes of E, FAC, Δn and how are they related to mono/conv/div E, ΔV, Kp, ΣP…. ?
>1000 events
2 km
4 km # #
S(FAC)
gyroradius
Johansson et al.

14. High-altitude signatures of ionospheric density depletions
T. Karlsson et al.
Expected correlation with constant ionospheric conductivity and no E// : En Bt
Instead sometimes, correlation [downward j// ] ~ En
, SH, MLT ~ 20
j// (mA/m2)
En (mV/m)
upward current
downward current
t (s)

15. From earlier simulations
Model – ionospheric modification by downward FACs
From earlier simulations
j//
Magnetosphere Jn
upward j// S
downward j//
Ionosphere En

16.
DBt En SP
j//
DBt En SP
j//

18. High-altitude signatures of ionospheric density depletions
T. Karlsson et al.
Expected correlation with constant ionospheric conductivity and no E// : En Bt
t (s)
Instead sometimes, correlation [downward j// ] ~ En
, SH, MLT ~ 20
j// (mA/m2)
En (mV/m)
downward current
upward current