The Dynamics of Auroral Absorption

Abstract

The earliest riometer studies of auroral radio absorption paid little attention to movements. The first overt reference to them is probably a single example reported by Kavadas (1962). Evidence of movements can be seen in the diagrams of some other early papers (Little and Leinbach, 1958; Holt et al., 1962) though the authors do not draw attention to them in the text. Thus, most of the earlier investigations of auroral absorption (AA) concentrated on questions such as the mechanism of radio absorption and the nature of the primary particles, the synoptics of time and place of its occurrence, and on relationships with other auroral and geophysical phenomena. Towards the middle of the 1960’s there were further reports of AA movements, based on time differences between the appearance of bursts of activity at geographically separated stations (Eriksen et al., 1964; Ansari, 1965; Little et al., 1965), and there has been an increasing concentration on the dynamics of AA since that time. As a result, it is now realized that nearly all absorbing regions are in motion, that the motions are largely systematic, and that they occur on the global scale — that is, involve both night and day sectors and include the whole width of the auroral regions in both hemispheres. Clearly this has been a significant development and there can be little doubt that studies of the dynamics of auroral absorption represent one of the most important aspects of riometer work now and for the immediate future.