Seasonal variation of auroral electron precipitation

Abstract

Global observations of nitric oxide obtained from the Student Nitric Oxide Explorer (SNOE) have been used to determine the density of nitric oxide in the lower thermosphere. A thermospheric model which takes into account all of the photochemical processes that produce and destroy nitric oxide has been used to deduce the flux of precipitating auroral electrons that produce nitric oxide. The results of this analysis allow us to infer the daily variability of precipitating electron energy deposition. The most important result of this paper is that there is a clear-cut minimum in the electron flux at the time of the summer solstice in both hemispheres. This seasonal dependence of precipitating auroral electrons supports the idea that auroral arcs are suppressed in the solar-illuminated hemisphere due to high ionospheric conductivity. The strength of the seasonal variations suggests that the bulk of the energy deposition may be due to discrete auroral events. Copyright 2004 by the American Geophysical Union.