Airborne observations of auroral precipitation patterns

Abstract

There are at least four distinct regions of auroral particle precipitation. The auroral oval and nightside proton aurora are well known; they are well separated in the evening sector and overlap in the morning sector. There is a zone of soft-electron precipitation at latitudes above the auroral oval where ∼0.5-kev electrons precipitate; no protons are observed in this region. Electron energies in this soft zone decrease systematically with latitude (for a given Kp). There is a zone of soft-electron (∼100–200 ev) and soft-proton precipitation at latitudes above the auroral oval near the midday meridian, and these particles probably come directly from the magnetosheath. No higher energy protons (as in the nightside proton aurora) were observed near midday, during quiet magnetic conditions.