Effects of high-latitude thermosphere heating at various scale sizes simulated by a nonhydrostatic global thermosphere–ionosphere model

Abstract

Using the University of Michigan Global Ionosphere–Thermosphere Model (GITM) variations of the high-latitude Joule and auroral heating with increasing spatial resolution and the resulting changes in the high-latitude thermosphere–ionosphere are studied. Additionally, the application of multiplicative factors artificially increasing the Joule heating in global thermosphere models is investigated by running simulations at low resolution, at high resolution, and then at low resolution again, with the Joule heating artificially increased to be similar to the value derived when running with high resolution. All simulations have been performed for December solstice conditions at constant low geomagnetic and moderate solar activity levels. Increasing the resolution from 5° longitude by 5° latitude to 2.5° longitude by 0.3125° latitude increases the high-latitude mean Joule heating by ∼ 40 % , partially by better capturing the peaks in the electric field. Although the Joule heating is increased, the global mean temperature is not altered significantly due to resulting adiabatic cooling. When the Joule heating is artificially increased in the low resolution simulations, the temperature increases more, due to the model inability to adequately capture the dynamical cooling. It is therefore suggested that artificially increasing the Joule heating may not be the best method for capturing the realistic temperature structure or the dynamics within the thermosphere.