A Study of Ionospherics at Macquarie Island

Abstract

Very low frequency radio emissions of natural origin, sometimes known as iono. spherics, recorded at Macquarie Island have been examined and grouped into classes. The diurnal variations of all classes show a non·uniform distribution with a peak shortly before local midday. The ionospherics appeared to fall into three groups as regards dependence on magnetic K·index. Strong correlations were discovered between values of emission frequency and K.index, for several classes of ionospherics. The roleof Cerenkov radiation in the generation of ionospherics is discussed. Suggested energy distributions are put forward to explain various classes of ionospherics. The magnetic associations and diurnal variation are explained on the basis of current geomagnetic disturbance theory. Ionospheric absorption is also considered to affect the diurnal variation. The phenomenon of" surf", as reported by Campbell and Pope, is discussed.