Longitudinal Variations of Geomagnetic Field and their Time Derivatives during Ionospheric Disturbance Dynamo over Africa and Asia

In this study, we present and discuss the response of horizontal (H) component of the Earth magnetic field, longitudinal profile during the ionospheric disturbance dynamo (Ddyn) and the rate of magnetic field (dH/dt) during 24-25 October 2011 geomagnetic storm in the African and Asian sector. Results revealed that the solar variation SR and the typical H-field at both longitude sectors exhibit higher magnitudes at the equatorial region that the mid-latitudes. At the time of SSC, the typical H-field exhibit higher magnitudes than the solar quiet variation SR across most of the latitudes in the African sector and only observable in the Asian sector at the midlatitude. The variation in the intensity of the SR and the typical H-field during the recovery phase is larger prior to the occurrence of the SSC. The difference could be attributed to the presence of the westward current that manifest as a difference in the typical H-field observed across all the latitudes. Higher rate of magnetic field (dH/dt) are obtain at the time of SSC in the African sector with Asian region exhibiting higher magnitudes during the main phase of the magnetic storm. Generally, both longitude sector show rate of change of magnetic field (dH/dt) during the recovery phase of the magnetic storm which are more noticeable in the African sector This implies that large dH/dt are not only associated to prompt penetration of the magnetospheric electric field (PPEFs) but can also be influenced by ionospheric disturbance dynamo (Ddyn) mechanism.