Analysis of Geomagnetic Storm Effects on Ionospheric Vertical Drifts over the East African Low Latitude Region

Abstract

The geomagnetic storm effect on ionospheric vertical E × B drift is analysed
using Communication/Navigation Outage and Forecasting System (C/NOFS)
Satellite data, magnetometer data, and solar wind data, over the East Afri-
can low latitude region during the period 2008-2015. We identified a total
of 608 corotating interaction region (CIR)-driven and 23 coronal mass ejec-
tion (CME)-driven geomagnetic storms in this study. Most of the CIR-driven
storms were observed during the declining phase of solar cycle 24 in 2015. The
CME-driven storms, on the other hand, were dominant during the near max-
imum phase of the solar cycle 24 in 2012. The C/NOFS satellite data was found
to be consistent with magnetometer observations in identifying both upward
and downward vertical E × B drift occurrence. The common result of analysed
CME-driven geomagnetic storms was enhancement in E × B drifts due to pres-
ence of eastward prompt penetrating electric fields (PPEFs) during the storm
main phase. There was also a decrease in E × B due to the decrease in hori-
zontal component of the magnetic field ( ?H ) during the recovery phases of
the CME-driven storms. This is a manifestation of downward E × B drifts as-
sociated with westward electric field, which is due to the disturbance dynamo
contribution. During CIR-driven geomagnetic storms, the storm’s main phases
were also dominated by downward E × B drifts associated with westward elec-
tric field, which is due to disturbance dynamo.