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