Analysis of geomagnetic data obtained at multi observatories near Syowa Station during the IMS (1976-1978)-Correlation of the location of auroral electrojet current with the aurora and the behavior of geomagnetic conjugacy -

Abstract

This report describes the movement of small scale auroral electrojet current regions and their relationships to spatial and temporal variation of visual auroras based on magnetic data at three ground stations [Syowa (69°00′S, 39°36′E, 30m a. s. l.), Unmanned (69°47′S, 41°35′E, 1470m a. s. l.) and Mizuho (70°42′S, 44°20′E, 2230m a.s.l.)]. Japanese Antarctic Research Expedition (JARE) party carried out this observation as a contribution to the International Magnetospheric Study (IMS) from 1976 to 1978. It was shown that ionospheric currents with no change in Z-component magnetic field variations corresponded to auroral luminous regions. This result suggests that the line current approximation is applicable to small scale auroral electrojet currents. Secondary, a conjugacy of polar substorm phenomena is examined with comparing magnetogram data obtained from three ground stations in Antarctica and with those from Leirvogur station (64°08′N, 21°47′W), Iceland in the northern hemisphere. During quiet periods, the conjugacy could not be identified due to poor correlation of magnetic field variations between Leirvogur and the three stations in Antarctica. On the other hand, during disturbed periods, the conjugate point of Leirvogur was located near the Unmanned station. Thirdly, the diurnal variation of magnetic conjugate point is examined with magnetogram data of antarctic three ground stations and two stations (Husafell and Leirvogur) of iceland. The conjugate point shifted toward the higher-latitude side from the evening (18h MLT) to the mid-night (00h MLT), while it shifted toward the lower-latitude side from the mid-night to the morning (08h MLT) hours. This result was consistent with the diurnal variation of the conjugate point calculated from the Tsyganenko-Usmanov model.