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 11 h36m-12h30m UT and l4h10m-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.

Temporal development of irregular magnetic pulsations occurring during low‐latitude auroras

“…In particular, it is necessary to investigate the irregular magnetic pulsations occurring during these auroras. In this paper, we refine and expand two previous papers, comprising a case study of irregular magnetic pulsations (Pil-2 and intervals of pulsations of diminishing periods (IPDP)) OCT [Higuchi, 1994[Higuchi, , 1995. Emphasis is placed on an analysis of the particle spectrum associated with low-latitude auroras and on convective growth rate modeling for the IPDP plasma wave events.…”

“…It is noteworthy that the low-latitude IPDP plasma wave event observed in association with the low-latitude aurora occurs while the magnetic field perturbations at GOES 6 and 7 begin to recover the dipole-like configuration from the more tail-like magnetic field configuration. Therefore the low-latitude IPDP plasma wave event observed at YNZ in association with the low-latitude aurora can be generated by the wave-particle interaction involving the temporal particle injection during the expansive phase of substorms [Higuchi, 1995]. More than 25 years ago, Roxburgh [1970] had found that IPDP plasma wave events observed on the ground occurred simultaneously with the increase in the magnetic field strength measured overhead at geosynchronous orbit.…”