Model simulations of the electrodynamics of the high latitude thermosphere and ionosphere with the magnetospheric input defined by statistical or empirical models

Abstract

The UCL-Sheffield thermosphere/ionosphere global numerical model has been used to compare the electrodynamic response to the various empirical and statistical representations of the magnetospheric input at high latitudes. Four electric field models and two auroral precipitation models have been chosen for moderately active geomagnetic conditions, and the numerical model run for December, high solar activity conditions. The empirical convection patterns have a strong BY dependence, and are 30% more intense than the statistical models. The simulations on balance favour the larger magnitudes when compared with observations of wind, temperature, and composition. The auroral precipitation models generate similar ionization rates in the upper thermosphere, and differ by 50% in the lower thermosphere. Joule heating rates can differ by a factor four, for nominally the same geomagnetic activity conditions, depending on the choice of model input and whether the influence of neutral winds are included. A second peak in Joule heating occurs on the dawn or dusk side of the polar cap for IMF-BY positive or negative respectively. Divergence of the height-integrated horizontal ionospheric current system generates the pattern of Region 1 and 2 field-aligned currents, and also has strong BY dependence.