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Timing analysis of a substorm event on January 29, 2008 observed by THEMIS: multiple intensifications, current disruptions and plasmoids.
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Timing analysis of a substorm event on January 29, 2008 observed by THEMIS: multiple intensifications,current disruptions and plasmoids. 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 ICS-9, May 6, 2008
CL G12 B E C C D GTL E D Mid-tail Near-Earth tail G12
Global energy assessment • 4 successive events: 2 pseudo-breakups 1 substorm including 2 intensifications Static pressure: Ps = Pm + P┴i (ESA) + P┴i (SST)
To To Xo C B Xo C B Xo: “detachment point” of the plasmoid Initial location of the disruption Differential timing analysis Event 1: V = 340 LB = 15 Xo = -6.8 DPs/Pso ~ 12 Event 2: V = 525 LB = 8.5 Xo = -9.5 DPs/Pso ~ 13 (km/s) (Re) (Re) (%) Vx (km/s)
Xo C B Blob, Ps BZ (Jacquey et al., 1991, Ohtani et al., 1992) To V1 ~ 640 km/s Xo1 ~ -13 Re V2 ~ 450 km/s Xo2 ~ -8 Re 3 successive V-shaped BZ signature associated with pressure decrease 3 successive tailward propagating current disruptions/reductions ?
Timing comparison near-Earth/mid-tail probes < 1’ 55 sec < 1’ 25 sec -2’43’’ -163 sec < 1’ 10 sec
Timing synthesis [X,Y] location: thD: -9.7 ; 1.4 thE: -8.5; 2.3 Event 1 Event 2 Event 3 Xo: -6.5 -9.5 -13/-8 (inferred from C and B) Tailward Earthward Earthward (Propagation inferred Dawnward Duskward Duskward from timing D/E) thD: Tailward ??? Earthward (Local propagation thE: Tailward ??? Earthward inferredfrom energetic ion anisotropy (not shown)
Conclusions (preliminary) • Overall consistency of the timing of the observed features • Quasi-periodic intensifications, T ~ 16 min. • Plasmoids/TCR • Initiated close to the Earth (R < 10 Re) • Clear TCR signature at 29 Re, but ambiguous ones at 18 Re (alternative: tailward propagating disruption) • Associated with dipolarisation and particle acceleration in the near-Earth tail • Speed: V ~ 350-550 km/s; Length: 8 – 15 Re • The main substorm • Initiated in the near-Earth tail (~13 Re and/or 8 Re) • Earthward propagating injection/dipolarisation • seems to develop by successive discrete steps • Lobe magnetic field changes consistent with tailward propagating current disruptions (or reductions) • Each event was associated with large amplitude flow oscillation at ~2 min in the near-Earth tail.
