THE AFRICAN EQUATORIAL IONIZATION ANOMALY RESPONSE TO THE ST. PATRICK'S
DAY STORMS OF MARCH 2013 AND 2015
Abstract
The ionosphere around the Equatorial ionization Anomaly (EIA) region
exhibits a complex dynamic and responds markedly to the
solar-magnetospheric energy and momentum. In this paper, the hourly
response of the EIA structure in the Africa to St. Patrick’s Day storms
of March 2013 and 2015 is investigated using data obtained from a chain
of GPS receivers located in the African region. The TEC variations were
characterized based on the convective magnetospheric dynamo fields, the
neutral wind circulation, and zonal electric fields. Generally, the
result indicates that the TEC variations were consistent with the
different directions of the interplanetary fields during the different
phases of the storms. We observed reverse EIA structures in the main
phase of the storm of March 2015, suggests to be related to the intense
PPEF and strong equatorward wind which imposed westward zonal electric
field at the equator. Similar equatorial peak observed during the
recovery phase is associated to DDEF, poleward wind and plasma
convergence. Furthermore, TEC variations also indicate hemispheric
asymmetries during the storms. During the main phase, the TEC is more
enhanced in the northern hemisphere during the storm of March 2013, this
was reversed during March 2015. We observed equatorial peak during SSC
period of the storm of March 2013, while EIA structures are generally
weak in March 2015 event. This may posit that ionospheric pre-storm
behaviour is better understood when the IMF-Bz and electric field are
weak. The observed distinctive response avowed the peculiarity in the
electrodynamics intricacy in the Africa sector.