A study of high-latitude E-field patterns using simple models with day-night ionospheric conductivity gradient

Abstract

Simple models with the effect of the day-night ionospheric conductivity gradient are used to discuss the high-latitude convective electric field pattern. The exponential function exp ( −x L ) is used to express the day-night variation in conductivity. Three types of models are used in this work: Model 1: The electropotential distribution is a sine function at the polar cap boundary if we neglect effects of region-2 field-aligned current and the conductivities enhancement within the auroral zone; Model 2: With two regions of field-aligned currents, and without conductivity enhancement in the auroral zone; Model 3: Both the two regions of field-aligned currents and the enhancement of conductivity within the auroral zone are taken into account. The comparison between the different models helps us to understand the convective pattern under different geomagnetic conditions. It also shows the combined effects of the field-aligned currents and the variation of the conductivities (both the day-night gradient and the enhancement within the auroral zone). The results can also offer reasonable explanations to some phenomena observed, such as the apparent discrepancy between different observations concerning the dawn-dusk asymmetry of the convective pattern, and some features of the field-aligned currents.