Variability of ionospheric irregularities over the longitudinal sectors of African equatorial/low latitude region during the geomagnetic storm of 17 March 2013

Abstract:

Variations of irregularities have been studied during the geomagnetic storm of 17 March 2013. The rate of change of TEC (ROTI) derived from 26 African GNSS receivers distributed into three longitudinal sectors; Eastern (25^o-40^oE), Western (3^oW-10⁰E) and Atlantic (16^o-5^oW) was used to monitor irregularities from 15 to 21 March 2013. Their latitudinal variations were studied over mean longitude 37^oE (Eastern sector) with coverage of 30^oS-30⁰N and resolution of 30 minute x 1 degree. Comparisons were made between stations located over the magnetic equator and towards the crests in all sectors. The H component of the Earth’s magnetic field obtained from ground based magnetometers was further used to compute ionospheric electric current disturbance (Diono). Diono was filtered to isolate contribution due to prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF). Over mean longitude 37^o, on pre storm days, patches of irregularities were observed at about 6-20^oN and 0-5⁰S geographic latitude. During the main phase, irregularities intensified and were more localized at about 10-22^oN and 2^oN-5^oS. During the recovery phase, they spread within 5^oS-15^oN but were more intense over the southern hemisphere. Longitudinally, during the main phase, no irregularities were observed over stations located at about 20^oS in the Eastern and Western sectors while they could be seen over those located toward the southern crest (8^oS). They were however, stronger (weaker) over the Western (Eastern) sector. For stations located at the trough and toward 18⁰N, the Eastern sector experienced irregularities while the Atlantic and Western sectors did not. During the recovery phase, irregularities were weaker (stronger) over the Western (Eastern) sector for stations located towards the crest in the southern hemisphere (8^oS). For those at the trough, they were stronger over the Atlantic in comparison to the other two sectors. For stations located at about 18⁰N, irregularities were inhibited over the Eastern and Atlantic sectors. These results highlighted the dependence of ionospheric irregularities on the location of the stations and local time of occurrence of southward turning of interplanetary magnetic field (IMF Bz) thus, on the configuration of storm time electric field during various storm phases over Africa.