Geomagnetic Storm Variation of Vertical Total Electron Content (VTEC) Over Some Euro-African Stations

Abstract

Geomagnetic storms are events which have physical effects on some ionospheric parameters that, to some extent,affects  the state and dynamics of the ionosphere  with important implications on GNSS applications. Here, the total electron content (TEC) of Brussels (50.80oN, 04.37oE), Madrid (40.43oN, 04.25oW) and Irkutsk (52.22oN, 104.32oE), which are all mid-latitude European stations are compared with Libreville (00.35oN, 09.67oE) and Lusaka (15.43oS, 28.32oE) which are equatorial and low-latitude stations respectively. This study is done over two geomagnetic storms that took place in the solstice period of 2004. Deviations of storm time VTEC from solar quiet (Sq) averages are calculated, analysed and presented. Similarities and differences of storm effects are observed in the European stations with enhancements and depressions. Diurnal solar quiet day variations showed high VTEC during the post-noon hours for all the stations. The VTEC deviations during storm time at Libreville lie within, for Lusaka it is. For the mid-latitude European stations, the deviations are lower such that  is recorded at Brussels while  is recorded for both Irkutsk and Madrid. Enhancement of VTEC during the daytime storm period is attributable to the super-fountain effect caused by the prompt penetration electric fields (PPEFs) into the ionosphere and magnetosphere while low VTEC at night-time is attributed to the process of recombination.   Understanding the behaviour of the ionosphere during geomagnetic storms is important and necessary for a better understanding of the applications of GNSS.