Investigating the Development of Abnormal Subauroral Ion Drifts (ASAID) During the Magnetically Quiet Times of October 2003

摘要

Appearing as inverted subauroral ion drifts (SAID) during magnetically disturbed and quiet times, the abnormal SAID (ASAID) is a recently reported phenomenon. Disturbed-time ASAID development can be explained with a magnetospheric cold-plasma-shoulder-hot-ring-current interface layer that generates an earthward (or inward) magnetospheric electric (E) field, which maps down to the ionospheric cold-plasma-trough-hot-ring-current interface layer as a southward (or equatorward) ionospheric E field. However, this plasmaspheric shoulder cannot develop under magnetically quiet conditions. Therefore, the quiet time ASAID development is still not clear and our main aim is to unravel its development. We analyze multisatellite and multiinstrument observations and show four scenarios demonstrating ASAID events during the magnetically quiet period of 9-11 October 2003. Results obtained for the longer 9-12 October 2003 time period provide observational evidence of the continuous presence of solar wind Alfven waves (i) driving dayside magnetopause and nightside magnetotail reconnections, (ii) bouncing back and forth in the coupled magnetosphere and ionosphere, and thus (iii) creating bouncing Alfven waves that ripple the plasma sheet's inner edge during the ASAID events investigated. These observational results suggest that the bouncing Alfven waves led to the development of a magnetospheric cold-plasma-ripple-hot-ring-current interface layer during these quiet times leading to quiet time ASAID development. Confirming this suggestion, we demonstrate and analyze 10 February and 5 March 1991 scenarios, depicting ASAID events, and invoke published magnetospheric cross-tail E_Y observations evidencing bouncing Alfven waves and plasma sheet rippling during the underlying energetic particle injection events.