Auroral Precipitation During the Bastille Day Storm Recovery 


Immel, T. J., Frey, H. U., Mende, S. B, Gerard, J. C., Hubert, B.,
Gladstone, R., Sandel, B. R., Forrester, T.

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 satellite. 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.