科研之友
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摘要
A fortuitous multisatellite observation of a dayside merging event driven by a sharp southward interplanetary magnetic field (IMF) turning illuminates several ionospheric particle and auroral reconnection signatures. Shortly after the southward IMF turning, as propagated from ACE, DMSP F13 observed a region equatorward of the cusp emptied of magnetospheric ions and bounded by two sharp intensifications of electron energy flux. The equatorward electron burst occurred at 74.4 degrees magnetic latitude. That is also both the boundary to which magnetospheric ions were depleted and to which magnetosheath ions appeared in a DMSP F12 satellite pass 4 min later. These latter ions evinced a low-energy cutoff, implying that about 4-5 min elapsed since merging. The equatorward electron burst observed by F13 reached an intensity of 8.6 ergs/cm(2) s, and thus must have produced a strong auroral signature. Indeed, Polar UVI observed a dayside auroral transient at the appropriate latitude and local time. This burst was likely Alfvenic (it was not monoenergetic (not associated with a quasi-static electric field)). The poleward electron burst observed by F13 (up to 4.6 ergs/cm(2) s), was at the equatorward edge of the old cusp and also had a broadband (Alfvenic) signature. Drift meter data on F13 indicates that the merging burst produced flow speeds up to 2 km/s and a 47 kV cusp contribution to the polar cap potential, of which 25 kV was in a narrow high-speed spike. Thus, this event probably constituted a significant fraction of the cross-polar cap potential.
- 出版日期2010-11-9
