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Ann. Geophys., 18, 1043-1053, 2000
www.ann-geophys.net/18/1043/2000/
© European Geosciences Union 2000
Polar patches observed by ESR and their possible origin in the cusp region
A. M. Smith, S. E. Pryse, and L. Kersley
Department of Physics, University of Wales, Aberystwyth, SY23 3BZ, UK
Correspondence to: S. E. Pryse
e-mail: sep@aber.ac.uk
Abstract. Observations by the EISCAT Svalbard radar in
summer have revealed electron density enhancements in the magnetic noon sector
under conditions of IMF Bz southward. The features were identified as
possible candidates for polar-cap patches drifting anti-Sunward with the plasma
flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar
and DMSP satellites, in a multi-instrument study, suggested that the origin of
the structures lay upstream at lower latitudes, with the modulation in density
being attributed to variability in soft-particle precipitation in the cusp
region. It is proposed that the variations in precipitation may be linked to
changes in the location of the reconnection site at the magnetopause, which in
turn results in changes in the energy distribution of the precipitating
particles.
Key words: Ionosphere (ionosphere-magnetosphere
interactions; plasma temperature and density; polar ionosphere)
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