<i>D</i>-region electron density profiles during auroras

Abstract

The purpose of this letter is to describe briefly the preliminary results of an analysis of multifrequency cosmic noise absorption data taken during auroral absorption events at College, Alaska. Single-frequency riometer data give no information as to the height at which the ionization causing the absorption occurs. We have shown, however [Parthasarathy et al., 1963], that cosmic noise absorption data taken on widely spaced frequencies can be used to derive ‘bestfit’ electron density profiles over the height range of approximately 30 to 75 km. Basically, the method depends on the fact that the ratio of absorption observed on different frequencies is a function of the ratio of the electron collision frequency v in the absorbing region to the angular radio frequency ω and therefore varies with the height of the absorbing layer. For v/ω≪1 (great heights) the standard f−2 dependence of the absorption is observed; the exponent decreases to zero as v/ω is increased to large values (i.e., for low heights).