Electron and Proton Auroral Dynamics

Data from the IMAGE Wide-band Imaging Camera (WIC),sensitive to far ultraviolet auroras and from the Spectrographic Imager (SI) channel SI12, sensitive to proton precipitation induced Lyman alpha, were analyzed during a high altitude orbit segment of the IMAGE spacecraft. This segment began during the expansive phase of a substorm. The aurora developed into a double oval configuration, consisting of a set of discrete poleward forms and a separate diffuse auroral oval equatorwards. Although IMF Bz was negative, considerable activity could be seen poleward of the high latitude arcs in the polar cap region. The optical signature of precipitating protons showed that the proton aurora was on the equatorward side of the diffuse aurora and there was a lack of intense energetic proton fluxes in the poleward arcs. A simultaneous FAST pass provided a diagnostic of the particle types in the various regions. These data showed that lower intensity protons were present throughout the entire double oval configuration but with insufficient intensity to produce aurora that could be observed by IMAGE. The FAST data also showed that the bright poleward discrete arcs were accelerated by electrostatic processes, and the wave accelerated electrons were located on the poleward edge of these features.