Meteor radar rates, geomagnetic activity and solar wind sector structure

Abstract

THERE is evidence which indicates^1–4 that the occurrence rate of meteor radar echoes varies inversely with solar cycle activity, this phenomenon can be explained^5–6 by a long-term variation in the atmospheric density gradient at the meteor ablation level. Inferred changes in the atmospheric properties are attributed to a long-term variation in the solar EUV radiation. Although the long-term, solar cycle changes in radar-determined meteor rates show an inverse correlation with sunspot numbers and other measures of solar activity, such correspondence is not readily evident in the day-to-day meteor radar data. One reason for this is the inability of most solar activity indices to measure the relevant solar parameters involved in short-term solar–terrestrial effects. The study of solar-influenced meteor rate changes on a time scale of days has, therefore, not received adequate attention. Evidence for a short-term dependence of meteor radar rates on geomagnetic activity and solar corpuscular radiation is presented here.