Auroral Precipitation during the Bastille Day Storm Recovery

The recovery period following the geomagnetic storm of July 15-16, 2000 is marked by rapid changes in auroral morphology and brightness in the sunlit hemisphere. These observations are made by the FUV and EUV imagers aboard the IMAGE satelite. Clear signatures of magnetospheric convection are observed in the motion of the auroral forms, indicating sunward convection of plasma in the polar cap under the strong northward component of the IMF. Precipitation is also observed equatorward of the auroral oval on the dayside in large diffuse arcs. Unlike previously observed detached proton arcs, this precipitation appears to have a significant electron component. Determination of the characteristic energies and fluxes of electrons and protons requires the proper removal of FUV airglow emissions, which in this case have been strongly affected by the recent magnetic activity. EUV images provide a very clear signature of these events, with practically no airglow contamination. With proper modeling, these EUV images could provide improvements to the characterization of the magnetospheric energy input to the thermosphere and ionosphere from space-based imaging.