Relation of electric field and particle precipitation in the polar cap region inferred from Akebono observations

Abstract

Akebono (EXOS-D) observations revealed that an electric field in the polar cap region was very irregular and an entire polar cap region was filled with many electron precipitation spikes when the interplanetary magnetic field (IMF) was directed northward. It was also found that the variation of the electric field was dominantly seen in the dawn-to-dusk (Ey) component while less variation was observed in the noon-midnight (Ex) component. Most electron precipitations were found in a region where a divE was negative. The integrated energy flux of the precipitating electrons was in the range from 0.01(erg/(cm)^2s) to 1(erg/(cm)^2s), which can produce auroral luminosity in the polar cap region. Though we have no simultaneous image data right now, it is likely that Akebono traversed multiple sun-aligned arcs.