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Distribution of auroral precipitation at midnight during a magnetic storm

1990; American Geophysical Union; Volume: 95; Issue: A5 Linguagem: Inglês

10.1029/ja095ia05p06051

2156-2202

I. Sandahl, L. Eliasson, Asta Pellinen‐Wannberg, G. Rostoker, L. P. Block, R. E. Erlandson, E. Friis‐Christensen, B. Jacobsen, H. Lühr, J. S. Murphree,

Earthquake Detection and Analysis

On the night of November 4, 1986, a very complex precipitation pattern was observed by Viking in the magnetic midnight sector over Scandinavia and Svalbard. The pass took place during a magnetic storm, and during substorm recovery phase. Going from north to south, the satellite first encountered a plasma region of BPS‐type (name derived from boundary plasma sheet) and then a region of CPS type (derived from central plasma sheet). Then, however, a new region of BPS‐type was traversed. The quite intense, most equatorward aurora corresponded to a plasma region which was not of ordinary CPS type but contained sharp quasi‐monoenergetic peaks. The high‐latitude midnight sector was totally dominated by eastward convection. The Harang discontinuity had passed northern Scandinavia the first time as early as 17 to 20 MLT, more than three hours before the Viking pass. It is suggested that the particle precipitation pattern and the general shape of the aurora as observed by the Viking imager can be explained in a natural way by the convection pattern. The northernmost BPS‐ and CPS‐type regions originated in the morningside convection cell, while the more equatorward population of BPS type had drifted in from the eveningside. The interpretation is supported by ground‐based measurements by EISCAT and magnetometers.