抄録
Based on the observation of low latitude ionosphere around 600km altitude by the Hinotori satellite, well-defined signatures of the ionospheric disturbances associated with substorm activities are found. In the wide area of the nightside equatorial region, a remarkable enhancement of local electron density takes place in response to the enhancement of the AE index, with a time delay shorter than the revolution period of the satellite (97min). The enhanced region is usually accompanied by several signatures which indicate the dynamical effects acting on the events, i.e. the development of the equatorial anomaly, longitudinal substructures and formation of the plasma bubbles. These signatures can be interpreted by dynamical uplift of the equatorial ionosphere. On the other hand, the equatorial anomaly is suppressed in dayside. Both of the nightside enhancement and the dayside suppression of the equatorial anomaly are induced simultaneously, although they are followed by rather different time sequential developments. The basic signatures of the ionospheric disturbance can be reasonably explained by dynamical effects of the disturbance electric field which is induced by substorm activities. The polarity of the disturbance electric field should be eastward in nightside and westward in dayside, and duration of the disturbance field is estimated to be about one hour or less.
