門倉/昭

講演予稿:
　１９８９年６月６日から７日にかけて起こったサブストームの解析を行っている。 今回はオンセット８分前からのグロースフェーズの最終段階に観測された特徴に ついて紹介する。

abstract:
　We are analyzing a substorm event which occurred in 6-7 June, 1989. An initial activity of the substorm started after an SC at 23 15 UT on 6 June, and an expansion phase onset (hereinafter simply called as onset) occurred at 00 42 15 UT on 7 June.. Before the SC, the IMF Bz stayed positive for at least 7hours, and ground magnetic activity was very quiet. After the SC, the IMF Bz turned and stayed negative during the course of the event. Hence this event was a typical one which occurred after a long quiescent period, initiated by theSC and following negative turning of the IMF-Bz, and whose onset occurred under a rather stable solar wind condition. As often observed in such a case, this substorm had a clear growth phase. In the last spring meeting, we showed several growth phase features observed with various ground based and satellite borne instruments after the SC. In this fall meeting, we will concentrate on the late growth phase features from about 8 minutes before the onset. About 8 minutes before the onset, a fast equatorward moving discrete aurora and HF scatter region appeared from higher latitudes and approached to the main oval and main scatter region, respectively. After that, the growth phase features were accelerated and equivalent current pattern in the nightside changed rapidly. About 5 minutes before, a north-south structured auroral form appeared from the higher latitudes, and extended toward the lower latitudes with a high speed of about 2.5 deg latitude/min in the Syowa all-sky video data. About 4 minutes before, an active discrete auroral activity and a clockwise flow pattern appeared around the Syowa zenith latitude in the Syowa all-sky and Halley HF-radar data, respectively. About 2 minutes before, the energetic electron flux in the LANL CPA data recovered or increased slightly, and Pi 2 range pulsations appeared in the GOES-7 magnetometer data whose oscillation period became longer and longer until the onset time. About 90 seconds before, equivalent current pattern above Halley started to change exponentially. About 35 seconds before, the UV auroral intensity started to increase around the onset location and the CNA increased in the Halley north and east riometers. At the onset, the Pi 2 range pulsations appeared in the Syowa, Asuka, and Hermanus induction magnetometer data, the D-component of the Halley magnetometer data changed abruptly, the D-component of the mid-latitude station magnetometer data showed an indication of the substorm current wedge formation, and all the Halley riometers showed abrupt increase of the CNA. The onset location should be within the discrete auroral oval at the higher latitude side of the Harang discontinuity in the ionosphere, and at the tailward side of the cross-tail current maximum location in the magnetosphere. We will talk about our interpretation for these data set.

キーワード:
サブストーム、電離層ー磁気圏結合

Keywords:
substorm, M-I coupling