SUPER DUAL AURORAL RADAR NETWORK OBSERVATIONS OF NEAR-NOON PLASMA CONVECTION AT SMALL INTERPLANETARY MAGNETIC-FIELD B-Z AND B-Y

Routine Super Dual Auroral Radar Network ionospheric plasma convection maps are used to study the structure of the near-noon convection esta blished at small interplanetary magnetic field (IMF) B-z and B-y. Duri ng such intervals, the influence upon convection of the quasi-viscous processes at the magnetopause is expected to be at least as important as the effect of magnetic field Line reconnection processes. It was fo und that, despite the small IMF B-z and B-y, there was a significant p lasma flow across the noon meridian, so that the convection throat wit h the antisunward plasma flow was shifted toward earlier magnetic loca l times (to similar to 1100 magnetic local time). It was also found th at the size and shape of the morning convection cell was similar to th e size and shape of the evening cell. It is argued that the shift of t he convection throat toward morning hours is most likely caused by the effects of the ionospheric polar cap plasma disconnection from corota tion with the ionospheric plasma on closed magnetic field lines. Other possible causes for the observed asymmetry are discussed.