A Case Study on Magnetic Signature of Ionospheric Disturbance Dynamo During an Intense Geomagnetic Storm on 6 August 2011

Coronal mass ejection (CME) occurs in the Sun’s corona that travels and reaches Earth’s magnetosphere, and it can trigger a geomagnetic storm. In this work, we presented a case study of a geomagnetic storm triggered by CME and observed the presence of ionospheric disturbance dynamo (Ddyn) at the equatorial station. Our analysis utilized CME data from the SOHO/LASCO CME Catalog, which contains information such as CME speed, solar source location, digital data, and the CME LASCO/C2 movies. The Disturbance storm time (Dst) index calculated from ground-based magnetometer data describes the geomagnetic storm phases. On the other hand, the variation of the Ddyn at the equatorial region was derived from the H component of Earth’s magnetic field. Four stations at the dip equator cover the longitude sectors of Asia (DAV and TIR) and Africa (AAB and ILR). This study shows that halo CME on 4 August 2011 triggered intense geomagnetic storms (Dst = − 115 nT) on 6 August 2011. During this geomagnetic storm, after a few hours of Dst peak, the signature of Ddyn can be clearly observed in two stations of the African sector (ILR and AAB), while no presence of Ddyn in two other stations (TIR and DAV) in the Asian sector.