Storm time changes in total electron content in ionosphere measured by low orbiting topside sounder

Abstract. A new experimental technique is presented for the determination of the total electron content (TEC) below a low-orbiting satellite. According to this technique TEC can be obtained using the segment of a topside ionogram that only contains the traces of signals reflected from the Earth's surface. Possibilities of this technique were demonstrated using MIR station topside sounding data at the night time for both quiet and disturbed ionospheric conditions, and in particular, during the 14 November 1998 storm. An interesting fact was revealed with the help of this technique: after a series of relatively strong storms the main ionospheric trough on 14 November 1998 was detected at an abnormally low geomagnetic latitude (~43°). During this study some spatial variations of TEC were registered that can be interpreted as a TID-type wave structure.