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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. 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.

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

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  1. Pseudo-breakups and substorm observed by THEMIS on January 29, 2008: timing analysis 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 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

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

  3. Large scale features

  4. No important change of SW velocity and pressure during the 01:00-03:00 UT period

  5. Ground-North America/MLT:21-17 Dipolarisaiton, ~02:57 GOES-12 BZ-GSM

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

  7. Mid-tail observations G12 B E C D Mid-tail Near-Earth tail Themis C: (-18, 1.4, -5.7)GSM, MLT = 23:42 Themis B: (-29, 2.2, -8.9)GSM, MLT = 23:43

  8. 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.

  9. Event 1 and 2: Plasmoids/TCR? Sauvaud et al., 1996, Jacquey et al., 1998, Jacquey, 2000 • Plasmoid-1: • Centres: DtCB ~ 3’25, V ~341 kmS/ • DtL(C) ~ 3’33, L ~ 11.4 Re • DPs ~ 44 pPa, DPs/Pso ~12% • DtL(B) ~ 4’39, L ~ 14.9 Re • Plasmoid-2: • MinBz: DtCB ~ 2’23, V~526 lm/s • DPs ~ 24 pPa, DPs/Pso ~13 % • DtL(B) ~ 1’42, L ~ 8.4 Re C B

  10. 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

  11. Near-Earth tail observations G12 B E C D Mid-tail Near-Earth tail 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

  12. Near-Earth tail observations

  13. Pseudo-breakups Main substorm Energetic ions and dipolarisation seem to propagate earthward

  14. Energetic ion anisotropy analysis 180 180 180 180 90 90 90 90 B 0 0 0 0 -90 -90 -90 -90 -180 -180 -180 -180 Z X 180° Y -90° 90° 0° Source located earthward f time Source located tailward f time passing from eastward to westward passing from tailward to earthward f f time time

  15. Energetic ion source located earthward of and close to the S/C Local tailward propagation of energetic ion front Local earthward propagation of energetic ion front Phase bunching (thin current sheet)? i:75 keV

  16. Westward local propagation Local tailward propagation of energetic ion front. Inverse energy dispersion i:75 keV

  17. Earthward/tailward propagation of the dipolarisations

  18. 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.

  19. 270° 90° Assuming DSL ~GSE Earthward initial location R < 10 Re Passing through the S/C

  20. 270° 90° Earthward initial location R < 10 Re Not passing through the s/c

  21. 270° 90° Tailward initial location R < 10 Re

  22. ACE GTL IMF: ~2 hour southward IMF period Northward turning at ~03:00 UT on GEOTAIL WIND

  23. Neutral line model Current disruption model

  24. K = 1/0.73 = 1.37 Ps_C computed with corrected Pthi Correction coefficient: K = 1.37

  25. Energetic ion anisotropy analysis 270 270 270 270° f f f 180 180 180 90° 90 90 90 0 0 0 time time time Source located tailward B Source located earthward Z X Y passing from earthward to tailward

  26. Ev1: earthward > tailward  Local tailward propagation? Ev2: source located earthward of the S/C, the front does not pass through the S/C Ev3: tailward > earthward  Local earthward propagation?

  27. Ev1: earthward > tailward Ev3: ??? Ev2: earthward > tailward  Tailward propagation, locally

  28. X Y 1.25 Re 0.9 Re

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