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Timing Analysis of JAN 29, 2008 Substorm Event by THEMIS

Multiple intensifications, current disruptions, and plasmoids observed during substorm event on January 29, 2008, using THEMIS data. Analysis includes differential timing, propagation, and associated signatures. Preliminary conclusions highlight key characteristics of the substorm event.

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Timing Analysis of JAN 29, 2008 Substorm Event by THEMIS

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  1. 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

  2. CL G12 B E C C D GTL E D Mid-tail Near-Earth tail G12

  3. Global energy assessment • 4 successive events: 2 pseudo-breakups 1 substorm including 2 intensifications Static pressure: Ps = Pm + P┴i (ESA) + P┴i (SST)

  4. 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)

  5. 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 ?

  6. Timing comparison near-Earth/mid-tail probes < 1’ 55 sec < 1’ 25 sec -2’43’’ -163 sec < 1’ 10 sec

  7. 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)

  8. 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.

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