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Event in 2002 with Cluster S/C at D~3500 km.

Determine the direction of propagation of early substorm signatures by comparisons between Geotail (~10Re) and Cluster (~18Re). Event in 2002 with Cluster S/C at D~3500 km.

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Event in 2002 with Cluster S/C at D~3500 km.

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  1. Determine the direction of propagation of early substorm signatures by comparisons between Geotail (~10Re) and Cluster (~18Re). Event in 2002 with Cluster S/C at D~3500 km. Where does substorm start; a case studyA.Roux, O.Holter, O.Le Contel, D.Fontaine, P.Louarn, J.A.Sauvaud, A.Fazakerley & C.Owen

  2. After 19:32: S/C get inside an expanding CS: dipolarisation at Cluster. Large amplitude fluctuations. Before 19:32: S/C outside the CS; early signatures (T~50s.) Early signatures Cluster inside CS 19:32 19:25

  3. Early signatures Cluster still outside CS.Early start: oscillations in Bx (&Bz increase) ~19:23 (9mn before dipolarization). remote sensing of activity inside CS?. InterS/C correlations along X and along Y=> small delay (<1sec). Lx&Ly larger than D (3600km) fast unguided mode 19:15 19:23

  4. Geotail in night sector at ~10 Re (-9.9, 0.3, -0.7). Injection at GEOTAIL, at ~19:22 on EPIC Sudden decrease of the modulus of Bx around 19:22 together with large amplitude oscillations of CS at Geotail. 19:30 19:20 19:20 19:30

  5. Possible scenario • Early breakup occurs near Geotail (~10Re) at ~19:22. • A tailward propagating dipolarization (~100km/sec) reaches Cluster ~10 mn later (Cluster penetrates in an expanding CS). • Dipolarization starts close to Earth and propagates tailward. • Yet small amplitude fast mode reaches Cluster first (at ~19:23) and provides a • Remote sensing of early substorm signature (corresponding to early dipolarization observed at Geotail).

  6. Conclusions and perspectives • We have presented results from a nice fortuitous conjonction between Cluster&Geotail. • THEMIS configuration will provide • Much more S/C conjunctions • 3 inner probes => much better coverage of inner PS. • 2 tail probes =>better assessment of radial propagation (fast flows&dipolarization). • Wide ground-based coverage.

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