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