Marc Hairston, Rod Heelis, (Center for Space Sciences, University of Texas at Dallas), Fred Rich (Phillips Laboratory, Geophysics Directorate)

On Janury 6th 1997 a coronal mass ejection (CME) occured on the sun which reached the Earth on January 10th and 11th, 1997 causing a massive geomagnetic storm. During this period there were two polar-orbiting DMSP weather satellites (F12 and F13) carrying the SSIES plasma instrument and the SSJ4 precipitating particle energy spectrometer on board. These instruments measure the bulk flow velocity, temperatures, chemical composition, and energy spectra of the precipitating ions and electrons of the ionospheric plasma at the 800 km altitude of the satellites. These data can be used to characterize the plasma environment in both the polar regions and lower latitude regions. We use these data to calculate the electric field and electrostatic potential along the flight track of the satellite. We will present the time history of the cross polar cap potential drop before, during and after the storm. We will also show the evolution of the patterns of the ion convection flow in the polar ionosphere throughout the storm and relate it to the observed IMF orientation. Last, we will use the convection reversal boundaries as observed by the satellites to estimate the size of the polar cap (open fieldline region) during this period.