High‐latitude ionospheric convection models derived from Defense Meteorological Satellite Program ion drift observations and parameterized by the interplanetary magnetic field strength and direction

Abstract

A series of new high‐latitude ionospheric convection models have been constructed using Defense Meteorological Satellite Program (DMSP) thermal ion drift measurements. The models are obtained by sorting cross polar cap electrostatic potentials into magnetic latitude/magnetic local time bins. A regression analysis of the potentials in each bin is then implemented for establishing the relationships to the interplanetary magnetic field (IMF) for three seasons: summer, winter, and equinox. A linear modeling formula for the ionospheric electrodynamics (LIMIE) yields a convection response to the average solar wind (i.e., the “quasi‐viscous” interaction) and to changes in the IMF By, Bz ≤ 0, and Bz > 0 components. The modeled convection is a superposition of the first two parameters with either the IMF Bz ≤ 0 or the Bz > 0 component. A global model is created by fitting the regression analysis results to a spherical harmonic function. The resulting DMSP‐based ionospheric convection model (DICM) is fully parameterized by the IMF strength and direction. With this model, ionospheric convection patterns can be generated for any IMF configuration during quiet to moderate geomagnetic conditions. We compare the DICM model with other available high‐latitude convection patterns organized by the IMF. The new elements in DICM are its quasi‐viscous and separate IMF‐dependent terms for both the northern and southern polar regions, which are not explicitly found in other ionospheric convection studies. The DICM's seasonal dependence and interhemispheric symmetry/asymmetry features show that the summer cross‐polar potentials are 10–15% smaller than the winter potentials. The latter is in agreement with the seasonal dependence of field‐aligned currents and with the voltage‐current relationship required for the proper magnetosphere‐ionosphere coupling.