institute of geophysics and planetary physics university of california, los angeles
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Institute of Geophysics and Planetary Physics University of California, Los Angeles. THEMIS observations at a substorm onset on March 1, 2008 - PowerPoint PPT PresentationTRANSCRIPT
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 1
Institute of Geophysics and Planetary PhysicsUniversity of California, Los Angeles
THEMIS observations at a substorm onset on March 1, 2008
A. Runov1, V. Angelopoulos1, X.-Z. Zhou1, V.A. Sergeev2, M. V. Kubyshkina2, S. Apatenkov2, I. Voronkov3, J. McFadden4, D. Larson4,
K.-H. Glassmeier5, U. Auster5, W. Magnes6, R. Nakamura6, C. T. Russell1, I. Mann7, S. Mende2, H. Frey2, L. Kepko8, and H.J. Singer9
1. IGPP/ESS, UCLA, Los Angeles, CA, USA2. St. Petersburg State University, St. Petersburg, Russia3. Athabasca University, Edmonton, Alberta, Canada4. SSL, University of California at Berkeley, CA, USA5. TUBS, Braunschweig, Germany6. IWF OEAW, Graz, Austria7. University of Alberta, Edmonton, Alberta, Canada8. SSC, University of New Hampshire, Durham, NH, USA9. NOAA Space Weather Prediction Center, Boulder, CO, USA
Correspondence to: [email protected]
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 2
P1
P2P3
P4G12
01:48:50 UT
GBAYG10
THEMIS GBO: Auroral onsets
P1
P3P4
G12
01:54:30 UT
G10
P2
1st (minor) intensification0148:42 UT GBAY
2nd (major) intensification0152:27 UT SNKQ
SNKQ
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 3
WIND (time shifted)
GBAY
DRBY
LOYS
KUUJ
CHGB
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 4
THEMIS and GOES observations 08-03-01/0100 – 0210 UT
01:48:50 UT
0148:42
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 5
Observations in the mid-tail PS
P2: X=-17.4 RE
Tailward fast flows Bz and By variations Ion & electron
energization
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 6
Observations in the mid-tail PS
P1: X=-22.7 RE
Same as at P2, but ~30 s later on
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 7
Timing of ion fluxes (SST and ESA) variations during the first
tailward flow P2
P1
SST: 50 – 200 keVESA: 5 – 21 keV
P2/THC: Tailward flux • 60 keV-Ion flux increases
at 0148:25 UT; • 190 keV flux increases at
0148:55 UT. Inversed Velocity
Dispersion (IVD, Sarafopoulos and Sarris, 1988)
SC are in the PS: IVD due to the acceleration by the inductive electric field (Taktakishvili et al., 1993)
SC are close to the acceleration region (1-3 RE)
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 8
Electron PA distributions at P1 and P2First tailward flow
0148:25
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 9
Observations in the near-Earth PS
P4: X=-8.0 RE ~6 min later than the
first activity in the mid-tail PS;
Magnetic field (and cross-tail current) reduction;
Dipolarization; Bursty Ion and
electron energization A step-like increase
of plasma density and pressure.
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 10
Observations in the near-Earth PS
P3: X=-9.3 RE The same as at P4,
but ~40 s later on Tailward propagation
of the step-like plasma pressure front at a velocity of 150 km/s.
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 11
P3 and P4 FGM measurements(field-aligned coordinates):
Main field (Bz) at P3 and P4 continuously increases (growth phase) until ~0955 UT
Perpendicular components, • δBy and δBx started at 0148:20
– 0148:40 UT, indicating outward FAC underneath the SC.
GOES 10 (PEN coordinates): Positive δBn (eastward!) at
0148- 0155 UT G10 was underneath of the FAC
GOES10, 12: Dipolarization at ~0154:20 UT
Magnetic field variations at P3, P4,GOES 10, GOES 12
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 12
2008-03-01/0140 – 0205 UTEvent Timing
0148:25 high-energy electron flux increase at P2 (transient reconnection?) 0148:25 ~60 keV ion flux increase at P2 (acceleration by the inductive E-field) 0148:40 dBy at P3, P4, G10 (FAC) 0148:42 minor auroral onset at GBAY (pseudo-breakup) 0148:45 Pi2 onset at GBAY 0148:45 Tailward fast ion flow, dBy & dBz at P2 0149:30 Tailward fast ion flow, dBy and dBz at P1 0152:21 Auroral onset at SNKQ (substorm) 0153:30 Dipolarization at G12 0154:20 Dipolarization at P4 0154:30 Tailward flow, dBy & dBz at P1 0154:40 Drop of Bt at P4 (cross-tail current reduction/disruption)
0155:00 Tailward flow at P2 0155:21 Auroral onset at KUUJ 0155:50 Dipolarization at P3 0155:50 dVy and dVz at P3 0155:50 Drop of Bt at P3
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 13
A Possible Scenario
The observations suggest a two-step development of the activity:
First step: An initial disturbance (probably reconnection) in the mid magnetotail (X~-15 - -17 RE) led to the particle acceleration, the Bz and By perturbations, the plasma bulk flow, and the FAC formation, associated with the first (minor) auroral activation (precursor). The FAC was, likely, generated by the Earthward reconnection outflow. The cross tail current in the near-Earth magnetotail (X~-9 RE) continued building up.
Second step: The rapid reduction (disruption) of the cross-tail current due to hot plasma pile-up, associated with the major onset, developed in the near-Earth plasma sheet. The second tailward flow, observed by P1 and P2, was, likely, generated by a process in the mid tail (probably reconnection), acting simultaneously with (and independent from) the current disruption, observed by P3 and P4 in the near-Earth plasma sheet.
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 14
Back up slides
GEM 2008 Summer Workshop, Zermatt, Utah, June 25, 2008 15
March 1, 2008 THEMIS major conjunction event
0148:50 UT0155:00 UT
01:54:30 UT