Pseudo-breakups and substorm observed by THEMIS on January 29, 2008: timing analysis

Many thanks to E. Penou (CESR) and T. Moreau (GFI) for developing data interface with the CL software

SWT meeting, UCLA, April 9-11, 2008

Jacquey C., O. LeContel, A. Tallet, 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

BC

DEG12

Mid-tail Near-Earthtail

G12

D

C

E

GTL

CL

21 22 23 00 01 02 030

10

20

30

40

MLT (HOURS)

L (R

e)

January 29, 2008, 02:45 UT

G12E D

C

B

Large scale features

No important change of SW velocity and pressure during the 01:00-03:00 UT period

Ground-North America/MLT:21-17

Dipolarisaiton, ~02:57

GOES-12BZ-GSM

Global energy assessment

4 successive events: 2 pseudo-breakups1 substorm including 2 intensifications

0

0.1

0.2

Ps: black Pm: green Pthi(ESA): blue Pthi(SST): red

B (

P1)

0

0.2

0.4

C (

P2)

0

0.5

1

D (

P3)

01:00 01:45 02:30 03:15 04:00 04:450

0.5

1

1.5

E (

P4)

-5

0

5B

Z-G

SE

(nT

)GEOTAIL/shift: 466 seconds [blue] ACE/shift: 3645 seconds [red]

01:00 01:45 02:30 03:15 04:00 04:450

1

2

Pdy

n (n

Pa)

01:00 01:45 02:30 03:15 04:00 04:45

BZ

(nT

)

January 29, 2008 GOES-12(Hp) THEMIS E(/2), D(/2), C, B(x2) GSM

G12

E

D

C

B

Static pressure: Ps = Pm + P┴i (ESA) + P┴i (SST)

Mid-tail observations

Themis C: (-18, 1.4, -5.7)GSM, MLT = 23:42

Themis B: (-29, 2.2, -8.9)GSM, MLT = 23:43

BC

DEG12

Mid-tail Near-Earthtail

-5

0

5B

Z-G

SE

(nT

)GEOTAIL/shift: 466 seconds [blue] ACE/shift: 3645 seconds [red]

01:00 01:45 02:30 03:15 04:00 04:450

1

2

Pdyn (

nP

a)

0.1

0.2

0.3

0.4January 29, 2008

PsC

(nP

a)

-5

0

5

10

BzC

(nT

)

0.1

0.15

0.2

PsB

(nP

a)

-2

0

2

BzB

(nT

)

01:00 01:45 02:30 03:15 04:00 04:450

5

10

XP

s/<

Ps>

(%

)

Mid-tail observations

Global decrease of energy density starts before at C (closest) than at B

“Dipolarisation” (BZ increase) also propagates tailward

The relative gradient of the static pressure remains roughly constant, except during the global dipolarisation event.

Event 1 and 2: Plasmoids/TCR?

Plasmoid-1:-Centres: tCB ~ 3’25, V ~341 kmS/tL(C) ~ 3’33, L ~ 11.4 RePs ~ 44 pPa, Ps/Pso ~12%tL(B) ~ 4’39, L ~ 14.9 Re

Plasmoid-2:-MinBz: tCB ~ 2’23, V~526 lm/sPs ~ 24 pPa, Ps/Pso ~13 %-DtL(B) ~ 1’42, L ~ 8.4 Re

C B

Sauvaud et al., 1996, Jacquey et al., 1998, Jacquey, 2000

0.3

0.32

0.34

0.36

0.38

January 29, 2008P

sC (

nPa)

-6

-4

-2

0

2

BzC

(nT

)

0.16

0.18

0.2

0.22

PsB

(nP

a)

-3

-2

-1

0

BzB

(nT

)

-1

0

1

2

3

BY

(nT

)C

UT (HOURS)

B

02:15 02:20 02:25 02:30 02:35 02:40 02:45 02:50

LogPth,i

-1

-2

Event 3 and 4: Large scale magnetic energy dissipation

2 successive major Ps decreases First one larger at C than at B Second one larger at B than C Energy dissipation sites develop more and more tailward

Event 3: the dipolarisation (BZ increase) propagates tailward V-shaped BZ signature Consistent with tailward propagating cross-tail current reduction

Multiple intensifications

0.3

0.32

0.34

January 29, 2008

PsC

(nP

a)

0

5

10

BzC

(nT

)

0.1

0.12

0.14

0.16

0.18

PsB

(nP

a)

-2

-1

0

BzB

(nT

)

0

2

4

6

8

BY

(nT

)C

02:45 02:55 03:05 03:15 03:25

UT (HOURS)

B

02:45 02:55 03:05 03:15 03:25

LogPth,i

-1

-2

Near-Earth tail observations

GOES-12: (-5, 4.2, -1.2),MLT = 21:21

Themis E: (-8.5, 2.3, -2.5)GSM, MLT = 23:02

Themis D: (-9.7, 1.4, -3.1)GSM, MLT = 23:28

BC

DEG12

Mid-tail Near-Earthtail

Near-Earth tail observations

Energetic ions and dipolarisation seem to propagate earthward

0

1

2D

-Pi (

nPa)

0

10

20

30

D-B

Z (

nT)

0

1

2

E-P

i (nP

a)

02:15 02:30 02:45 03:00 03:15 03:30

10

20

30

40

E-B

Z (

nT)

Pseudo-breakups Main substorm

Energetic ion anisotropy analysis

time

time

time

Source located tailward

Source located earthward

passing from tailward to earthward

-180-90

090

180

-180-90

090

180

-180-90

090

180

90°-90°

B

XY

Z

180°

0°

time

passing from eastward to westward

-180-90

090

180

Phase bunching (thin current sheet)?

Local tailward propagation of energetic ion front

i:75

keV

Energetic ion source located earthward of and

close to the S/C

Local earthward propagation of energetic ion front

i:75

keV

Local tailward propagation of energetic ion front.Inverse energy dispersion

Westwardlocal

propagation

02:15 02:30 02:45 03:00 03:15 03:30

BZ

(nT

)January 29, 2008 GOES-12(Hp) THEMIS E(/2), D(/2), C, B(x2) GSM

G12

E

D

C

B

Earthward/tailward propagation of the dipolarisations

0.220.240.260.280.3

0.32

January 29, 2008

PsC

(nP

a)

-1

0

1

BzC

(nT

)

0.16

0.18

PsB

(nP

a)

-2

-1

BzB

(nT

)

02:45 02:48 02:51 02:54 02:57 03:00

3

4

5

XP

s/<

Ps>

(%

)

January 29, 2008: preliminary conclusions

For all events:-In the near-Earth tail, the dipolarisation, magnetic turbulence and energetic ion flux enhancements propagates earthward (large scale trend)-Low frequency (2-3 minutes) flow oscillations observed in near-Earth tail-The global development of the dissipation events seem to progress by steps, via successive local and discrete intensifications (Lopez et al., 1993)

Pseudo-breakups:-Small plasmoids observed first in the mid-tail, before the energetic ion enhancements and dipolarisation in the near-Earth tail Main substorm:-Energetic ion enhancements and dipolarisation are observed first in the near-Earth tail the current disruption is likely the cause of the global energy dissipation- The magnetic signatures in the mid-tail are consistent with a tailward propagating cross-tail current disruption.

0.220.240.260.280.3

0.32

January 29, 2008

PsC

(nP

a)

-1

0

1

BzC

(nT

)

0.16

0.17

0.18

0.19

PsB

(nP

a)

-2.5

-2

-1.5

-1

BzB

(nT

)

02:45 02:48 02:51 02:54 02:57 03:00

3

4

5

XP

s/<

Ps>

(%

)

90°270°

Earthward initial locationR < 10 Re

Passing through the S/C

Assuming DSL ~GSE

90°270°

Earthward initial locationR < 10 Re

Not passing through the s/c

90°270°

Tailward initial locationR < 10 Re

ACE GTL

WIND

IMF:~2 hour southward IMF period

Northward turning at ~03:00 UT on GEOTAIL

Neutral line modelCurrent disruption model

02:15 02:20 02:25 02:300.3

0.32

0.34

Ps

(nP

a)January 29, 2008

B (T = -185 s)

C

02:15 02:20 02:25 02:30-4

-2

0

2

4

BZ

(nT

)

B (T = -195 s)

C

0 0.05 0.1 0.15 0.2 0.25 0.3 0.350

0.05

0.1

0.15

0.2

0.25

0.3

0.35TH-C 01:00-02:30

Pm

(nP

a)

Pthi[ESA+SST] (nPa)

Pm = -0.73 Pthi + 0.26

0

0.1

0.2

Ps: black Pm: green Pthi(ESA): blue Pthi(SST): red

B (

P1)

0

0.2

0.4

C (

P2)

0

0.5

1

D (

P3)

01:00 01:45 02:30 03:15 04:00 04:450

0.5

1

1.5E

(P

4)

Ps_C computed with corrected PthiCorrection coefficient: K = 1.37

K = 1/0.73 = 1.37

Energetic ion anisotropy analysis

90°270°

B

X

Y

Z

090

180270

time

090

180270

time

090

180270

time

Source located tailward

Source located earthward

passing from earthward to tailward

Ev1: earthward > tailward Local tailward propagation?Ev2: source located earthward of the S/C, the front does not pass through the S/CEv3: tailward > earthward Local earthward propagation?

Ev1: earthward > tailward Ev3: ???Ev2: earthward > tailward

Tailward propagation, locally

X

Y

1.25

Re

0.9 Re