Is All v*Bz Equal?

Solar wind electric field, v*Bz, is generally viewed to be the major driver of magnetospheric activity. A major diagnostic of magnetospheric activity is the potential imposed on the ionosphere. In this study we examine if, in fact, the ionospheric potential is the same for similar values of v*Bz or whether the average potential depends on how big the v and Bz are relative to each other. We use data from DMSP spacecraft collected during periods when v*Bz is less than 3 mV/m, in order to avoid the effect of polar cap potential saturation. Global MHD models suggest that there should be a difference in the magnetospheric response. We will present our findings from the data.