Analysis of the ionospheric cross polar cap potential drop and electrostatic potential distribution patterns during the January 1997 CME event using DMSP data

On 6 January 1997 a coronal mass ejection (CME) occurred on the sum produci ng a magnetic cloud in the solar wind that passed the Earth on 10-11 Januar y 1997 and caused a geomagnetic storm. During this period there were two po lar-orbiting DMSP spacecraft (F12 and F13) at 840 km carrying the SSIES pla sma instruments on board, which measure the bulk flow velocity of the therm al ions of the ionospheric plasma. These data are used to calculate the ele ctric field and electrostatic potential along the flight track of the space craft in the polar regions. The time history of the observed total cross po lar cap potential drop for this event is presented along with comparisons t o the estimates from the Weimer model and observations of the aurora from t he UVI instrument on the POLAR spacecraft. A surprisingly large potential d rop of 235 kV is observed at one point and appears to be the result of a pr essure pulse in the solar wind triggering an enhancement of the geomagnetic activity. An examination of the electrostatic potential distribution patte rns in the polar ionosphere during the event is also presented. (C) 1999 El sevier Science Ltd. All rights reserved.