Near-Earth substorm features from multiple satellite observations

Journal of Geophysical Research 05/2008; 113(A7). DOI: 10.1029/2007JA012738
Source: OAI


This paper was published as Journal of Geophysical Research, 2008, 113, A07S26. Copyright 2008 American Geophysical Union. It is available from Doi: 10.1029/2007JA012738 Metadata only entry We investigate a substorm on 3 October 2004 during which 11 satellites were located in near-Earth magnetotail (X GSM > −10 R E). Double Star 1 (TC-1), Cluster, and LANL-97 satellites were closely aligned in the dawn-dusk direction (<1 R E apart) for this conjunction. After substorm expansion onset, TC-1 observed plasma sheet thinning at X ≈ −5.5 R E and later detected signature of plasma flow shear that may be associated with an auroral arc. Analysis of the dawn-dusk magnetic perturbations from GOES-10 and Polar suggests that these could be caused by a substorm current system consisting of not only the azimuthal closure of field-aligned currents (the substorm current wedge) but also the meridional closure of field-aligned currents. The temporal sequence of substorm activity (particle injection, current disruption, and dipolarization) revealed by these satellites indicates that the substorm expansion activity was initiated close to the Earth and spread later to further downstream distances. Furthermore, TC-1 and Cluster data show that there is no close relationship between some dipolarizations and Earthward plasma flows in the near-Earth region. The overall development of substorm activity is in agreement with the near-Earth initiation model for substorms. A temporal evolution of the magnetic field reconfiguration and plasma boundary motion during this substorm is constructed from these observations.

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    Journal of Geophysical Research Atmospheres 07/2008; 113(A7). DOI:10.1029/2008JA013146 · 3.43 Impact Factor
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    ABSTRACT: We investigate in detail the time history of substorm disturbances in the magnetotail observed during a major tail conjunction of Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites on 29 January 2008, 0700–0900 UT. During this interval, all THEMIS satellites were closely aligned along the tail axis near midnight and were bracketed in local time by GOES 11 and 12. The radial distance covered ranges from the geosynchronous altitude to ∼30 RE in the tail. This interval consists of three activations detected by the THEMIS satellites with good ground all-sky-camera observations of auroral activity. The first activation is a small substorm with spatially limited disturbance in the tail. The onset arc was equatorward of an undisturbed arc. The second activation is a moderate size substorm with the onset arc also being equatorward of an undisturbed arc. The third activation is an intensification of the substorm with its onset indicated by the second activation. The active auroral arc for this intensification was near the poleward boundary of the auroral oval. Analysis of these observations indicates that the first activation is a small substorm initiated in the near-Earth plasma sheet and does not involve magnetic reconnection of open magnetic field lines. Magnetic reconnection on closed field lines can be ruled out for this substorm because it cannot generate the observed high-speed plasma flow. The second and third activations are part of a moderate size substorm initiated also in the near-Earth plasma sheet, with a subsequent substorm intensification involving activity initiated tailward of ∼30 RE. Overall, the time history of substorm activity for these two substorms is consistent with the near-Earth initiation model.
    Journal of Geophysical Research Atmospheres 12/2008; 113. DOI:10.1029/2008JA013424 · 3.43 Impact Factor
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    Journal of Geophysical Research Atmospheres 09/2009; 114(A9). DOI:10.1029/2009JA014064 · 3.43 Impact Factor
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