Reverse convection potential saturation during northwardIMF under various driving conditions

摘要

We report the results of an investigation of the reverse convection potentials in thedayside high-latitude ionosphere during periods of steady northward interplanetarymagnetic field (IMF). While it has been demonstrated that the reverse convectionpotentials exhibit saturation behavior, an investigation into how the saturated reverseconvection 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 datapropagated to the bow shock when the IMF is northward and when various drivingparameters are stable for more than 40 min. We then use bin-averaged SuperDARNDoppler radar velocity data to apply a spherical harmonic fit to calculate the averagepotential pattern for various driving conditions. Results show that the saturated reverseconvection potential during northward IMF is substantially lower than during southwardIMF (as expected), but the strength of the saturation electric field at a particular locationis comparable during northward IMF to what it is during southward IMF. Seasonaldependence and dependence on the Alfvenic Mach number and solar wind are alsoinvestigated. It appears that the reverse convection potential demonstrates the opposite ofwhat is expected for seasonal dependence, and that the Alfvenic Mach number is notthe fundamental driver of its saturation.