Low‐latitude ionospheric disturbances: Results for March 22, 1979, and their general characteristics

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Abstract
Low‐latitude ionospheric disturbances, which were characterized by severe scintillations in the C‐band range accompanied by complex dynamical behavior of the low‐latitude ionosphere, were examined, taking into consideration previous results. From the analyses of foF2 and h′F data, these disturbance events are found to be characterized by a two‐stage process. During the first stage, which starts during the magnetospheric energy storage process before the onset of substorms, h′F begins to increase simultaneously at all observing stations due to eastward electric fields penetrating from the magnetosphere. At subequatorial stations, increases of foF2 follow as a signature of enhancements of the equatorial anomaly. During the second stage, values of h′F increase again, indicating a motion from north to south, with no increase of foF2. In this stage, dynamical effects including neutral winds become important, as well as electric fields. In addition, it is shown from the analysis of one year's data for 1978 that the occurrence of disturbance events as presented in this paper is a general feature in the evening section under the condition of ring current developments.