Reverse convection potential saturation during northward IMF under various driving conditions

Abstract

We report the results of an investigation of the reverse convection potentials in the dayside high-latitude ionosphere during periods of steady northward interplanetary magnetic field ( IMF). While it has been demonstrated that the reverse convection potentials exhibit saturation behavior, an investigation into how the saturated reverse convection cells respond to various driving conditions has not yet been performed. We use the OMNI database from 1998 to 2007 to search for events in solar wind data propagated to the bow shock when the IMF is northward and when various driving parameters are stable for more than 40 min. We then use bin-averaged SuperDARN Doppler radar velocity data to apply a spherical harmonic fit to calculate the average potential pattern for various driving conditions. Results show that the saturated reverse convection potential during northward IMF is substantially lower than during southward IMF ( as expected), but the strength of the saturation electric field at a particular location is comparable during northward IMF to what it is during southward IMF. Seasonal dependence and dependence on the Alfvenic Mach number and solar wind beta are also investigated. It appears that the reverse convection potential demonstrates the opposite of what is expected for seasonal dependence, and that the Alfvenic Mach number is not the fundamental driver of its saturation.