Latitudinal Dependence of Ionospheric Responses to Some Geomagnetic Storms during Low Solar Activity

The Latitudinal dependence in the response of the Ionospheric F 2-layer electron density ( NmF 2) and peak height ( hmF 2) to three geomagnetic storms of May and August 2010 has been examined. The data-sets used for the study were obtained from Ilorin, Nigeria (1.87° S/76.67° E), San Vito, Italy (34.68° N/90.38° E), Hermanus, South Africa (42.34° S/82.15° E), and Pruhonice, Czech Republic (45.66° N/90.38° E) geomagnetic coordinates. The quiet time result shows that the rise in NmF2 began earlier at San Vito, followed by Pruhonice. The rate of ionization was observed to be highest in Ilorin, while, the rate of decay in NmF 2 is faster at Hermanus. For disturbed NmF 2 condition, remarkable similarities in the NmF 2 responses during geomagnetic storms were recorded from Hermanus in the mid-latitude and Ilorin, an equatorial station. NmF 2 enhancements (>6 hours) that is consistent with the increase in hmF 2 were observed at all the mid-latitude stations during the main phase of the 02 May, 2010 storm, without any noticeable change over ILN. Similarly, 12 hours of positive phase was observed at ILN and HMN, with 30 hours of NmF 2 depletions at PRN and SVT during the recovery phase. ILN is in the equatorial Trough, so most of the NmF 2 produced at this region is lifted to the higher latitudes by the fountain effect during the main phase. The suppression of the zonal electric field at ILN is responsible for the NmF 2 enhancement during the recovery phase, while the mid-latitude responses have been attributed to the effect of the thermospheric winds and neutral composition changes.