Electron energy deposition in the middle atmosphere

Abstract

Spectra of locally precipitating 36‐ to 317‐keV electrons obtained by instrumentation on the S3‐2 satellite are used to calculate energy deposition profiles as a function of latitude, longitude, and altitude. In the 70‐ to 90‐km altitude, mid‐latitude ionization due to these precipitating energetic electrons can be comparable to that due to direct solar H Lyman α. At night, the electrons produce ionization more than an order of magnitude greater than that expected from scattered H Lyman α. Maximum precipitation rates in the region of the South Atlantic Anomaly are of the order of 10−2 erg/cm² s with a spectrum of the form j(E) = 1.34 × 105 E−2.27 (keV). Southern hemisphere precipitation dominates that in the north for 1.1 < L < 6 except for regions of low local surface field in the northern hemisphere. Above L = 6, local time effects dominate; i.e., longitudinal effects due to the asymmetric magnetic field which are strong features below L = 6 disappear and are replaced by high‐latitude precipitation events which are local time features.