The day-to-night ratio of cosmic noise absorption during polar cap absorption events

Abstract

Riometer observations at a pair of nearly-conjugate stations inside the north and south auroral zones have been analyzed during periods of polar cap absorption in 1961. It is found that the absorption of cosmic radio noise is nearly the same at the two stations provided they are under similar conditions of solar illumination, indicating similarity of the incoming particle flux at conjugate points. Using data from both stations, the day/night absorption ratio is found to have a median value of 5.3 during magnetically-quiet periods.