IMF Control of High Latitude Electromagnetic Energy Flux

Electromagnetic energy flux is the dominant magnetospheric energy input to the dayside high latitude ionosphere-thermosphere system but it is difficult to evaluate its distribution. We use electric field estimates from SuperDARN observations and magnetic field observations from Iridium to obtain distributions of electromagnetic energy flux for a range of solar wind/IMF to characterize the variation in the distribution of energy input with driving conditions. Comparisons with DMSP derived estimates of Poynting flux along the DMSP track are used to quantify the uncertainties in the results. The distributions vary dramatically with the IMF in concert with variations in the large scale current distributions. The largest energy flux occurs between the dayside large scale currents. For strongly southward IMF, the energy flux generally has two maxima pre and post noon with a moderate flux around the auroral oval and over the polar cap. In the northern hemisphere for southward IMF but with a strong Y component, the energy flux increases in intensity and develops an arc corresponding to the convection driven by magnetopause reconnection. For positive IMF BY, this arc of energy flux extends from dusk to noon and crosses the nominal cusp region and extends into the polar cap. For negative IMF BY the arc extends from dawn to noon. The results suggest that the strongest energy flux in the cusp region occurs not for purely southward IMF but when the IMF BY component is strong. Also, since the convection associated with this energy flux has approximate mirror symmetry in the opposite hemisphere this IMF dependence will lead to asymmetric hemispherical distributions in the input energy flux.