Consequences of using simple analytical functions for the high-latitude convection electric field

The authors have developed analytical functions to represent the convection electric field of Heppner and Maynard (1987), which are realistic representations of the field. The functions include an explicit variability with geomagnetic activity for southward interplanetary magnetic field (IMF). They have used a simple computer algorithm to model the ionosphere and investigate the consequences of using the Heppner-Maynard analytical functions for the high-latitude convection electric field. The Heelis et al (1982) model, which has been widely used by investigators with computer simulations of the magnetosphere, ionosphere and/or thermosphere, is used here to provide a comparison. The Heppner-Maynard functions improve on the simple Heelis function for southward IMF. The Heppner-Maynard functions yield reasonable configurations and magnitude for Joule heating and field-aligned currents for a southward IMF. The Heelis model may or may not yield reasonable results depending on the input parameters. The major differences between the Heppner-Maynard functions and the Heelis function for southward IMF are for regions near (1) the dayside cusp, (2) the Harang discontinuity and (3) the subauroral latitudes. In general, the Heppner-Maynard functions yield results that more closely compare with other investigators. For northward IMF, the functional representations of the Heppner-Maynard do not reproduce the field-aligned currents in the polar cap which have been referred to as the NBZ current system