Satellite Particle Observations and Coincident Auroral-E Ionization.

Abstract : Using data taken during coordinated flights of the AFGL Airborne Ionospheric Observatory and the ISIS-2 Satellite, a comparison has been made between the particle spectrum of the continuous (diffuse) aurora and the properties of the auroral-E region with the following results: Most electron differential number spectra of the diffuse aurora may be represented as Maxwellians with characteristic energy between a few hundred eV to a few keV; this characteristic energy increases with the pitch angle to a maximum value of 90. Over the diffuse aurora, the angular distribution of electron energy flux is isotropic only pear the peak of precipitation. At latitudes above and below the peak, the energy flux at the edge of the loss cone may exceed that near the local field line by as much as a factor of two. Integration of individual spectra over the loss cone produces a composite Maxwellian distribution which may be used to estimate the electron energy deposited in the E-region. The procedure underestimates the energy by about 20%. Although the continuous (diffuse) aurora is a relatively stable phenomenon, enhancements in intensity of the incident electrons occur on a time scale of a few seconds. It has not been determined whether these variations represent temporal or spatial changes. Within the energy range 10 eV to 15 keV the electron population accounts for 80 - 90% of the particle energy deposited into the E-region.