Global cause of localized high latitude aurora

The FUV instrument on IMAGE frequently observes a very localized, spot-like aurora at high latitudes poleward of the dayside auroral oval and the cusp. The absence of simultaneous proton aurora suggests a pure electron precipitation, which was confirmed by a few conjugate FAST observations. This aurora occurs during northward IMF conditions with very low solar wind density (dynamic pressure). Additionally, there is a preference of negative IMF B_x conditions, and B_y has to be positive. These external conditions suggest reconnection at the high latitude magnetopause as the driving mechanism for this phenomenon. During the first two years of IMAGE-FUV operations a clear seasonal dependence was found with frequent and long-lasting occurrence of the spot-like aurora during northern hemisphere summer, and extremely few events during northern winter. We will describe how the seasonal changes of the dipole tilt, solar illumination and ionospheric conductivity influence the local occurrence and intensity of the electron precipitation.