Possible multiple acceleration sites during a substorm event :
1st March 2008
1h45 – 2h10
A. Tallet, C. Jacquey, O. Le Contel, H. Frey, V. Génot, P. Louarn, G. Fruit, B. Lavraud, J.A. Sauvaud, A. Roux, V. Angelopoulos, D. Sibeck, J.P. McFadden, D. Larson, U.
Auster, H. Singer
P1 P2P3
P4GOES-12
P5
Geotail
01:55:00 UT
P1P2
P3P4
GOES-12
Large scale features
Solar Wind ?
No significative variation of velocity and pressure
Substorm
Mid Tail Observations
01:49:23 01:55:11
Mid Tail Observations
01:49:23 First tailward flow onset & magnetic perturbation
01:55:11 Second perturbation magnetic
→ solitary By perturbation
→Bz similar to plasmoid/Xline
01:48:32 01:54:45
01:48:32 First tailward flow onset & magnetic perturbation01:54:45 Second perturbation magnetic
→ Bz similar to plasmoid BUT By → vflow~300 km/s
Mid Tail Observations
Near Earth Observations
01:55:16
01:55:16 B N T
ESA Flow
→ Bz increases & vy<0
Near-Earth Tail Observations
01:54:47
01:54:57 B N T ESA flow
→ Bz increases & vy<0
Near-Earth Tail Observations
01:56 ± 30s01:54 ± 30s
GOES-12 ?
Near-Earth Tail Observations
FirstEvent ?
Second Event ?
Quasi-simultaneous, X ~9 Re, t ~1-6 s
1: C(P2), 01:48:322: B(P1), 01:49:02
Tailward propagation from C to B
V ~1120 km/s
The perturbation was detected close to
the neutral sheet at both locations
No significant counter part observed
at D, E and GOES-12
• Tailward flow in the mid tail (C and B) : Vflow << Vpropagation → a wave rather than a struture
First Event
1: C(P2), 01:54:452: E(P4), 01:54:463: B(P1), 01:55:114: D(P3), 01:55:165: G12, 01:54 ± 30s ?
01:56 ± 30s ?
Tailward propagation from C to B:
V = ~ 1300 km/s
Perturbations have been detected
quasi-simultaneously at C and E There is 1 source between both
fortuitously initiated at a location such
as: Ve.dt = -Vt.dt Or There are 2 sources (likely
coupled)
Significant delay from E to D the
source is very localised
Second Event
Tailward propagation
Earthward propagation
?
• Tailward flow in the mid tail (C and B) : Vflow << Vpropagation → a wave rather than a struture
First hypothesis : one source
Tailward flow
→ Vflow ~ 300km/s
propagate tailward at
Vprop ~ 1300km/s
01:56 ± 30s
Earthward propagation
1: C(P2), 01:54:452: E(P4), 01:54:463: B(P1), 01:55:114: D(P3), 01:55:16
5: G12, 01:56 ± 30s ?
First hypothesis : one source
01:54 ± 30s Tailward flow propagating tailward
1: G12, 01:54 ± 30s ?
2: C(P2), 01:54:452: E(P4), 01:54:463: B(P1), 01:55:114: D(P3), 01:55:16
• One source between G12 and
TH-E, propagating tailward
(azimutaly) up to TH-D
• Quasi-simultaneous effect on C
and E
• Very slow propagation between
E and D : ~110 km/s
Scenario not very consistent
Second hypothesis : two sources!
Sources coupled !
01:54 ± 30s
1: G12, 01:54 ± 30s ?
2: C(P2), 01:54:452: E(P4), 01:54:463: B(P1), 01:55:114: D(P3), 01:55:16
• Two sources : one near to
G12 and one near to C
• Sources coupled because
quasi-simultaneous between C
and E
01:54:33
01:54:45
01:54:54
01:55:12
01:55:39
01:55:51
01:55:54
01:55:57
01:56:00
01:56:03
01:54
01:56:12
01:56:15
01:56:18
01:56:21
Conclusion
• Multiple sources ?
Coupled ?
• Nature of the perturbation on the tail satellites ? Wave ?
|By| > |Bz|
vflow << vpropagation
• Upcoming Analysis steps:
- Precise timing on GOES-12
- Local expansion of the acceleration region on D and E
- Ground data analysis