IPDP Plasma Wave Events Observed in Association with Low Latitude Auroras

Abstract

A case study of IPDP (Intervals of Pulsations of Diminishing Period) observed in association with low-latitude auroras is reported. Visible red auroras were detected twice in the time intervals of 11h36m-12h30m UT and 14h10m-14h30m UT on October 21, 1989. Simultaneously there were two rapid northward excursions of the H-component magnetic perturbation with the magnitude of more than 150 nT. The IPDP plasma wave events were observed at Yonezawa during the low-latitude auroras. The energy source of the IPDP plasma wave event is inferred to be the wave-particle interaction involving the asymmetric ring current oxygen ions at the bulge region of the plasmapause during the expansive phase of substorms. The frequency increase is explained in terms of a decrease of energy of the oxygen ion stream while the asymmetric ring current decays.