The cause of an extended recovery of ICME induced extreme geomagnetic storm: a case study

Abstract

Geomagnetic storms are very crucial phenomena during the severe space weather conditions, which directly or indirectly affect communication, navigation, transportation, power grid, and satellite electronic systems. They are usually caused by coronal mass ejections (CMEs) and/or corotating interaction regions (CIRs) of interplanetary space. The Earth’s magnetic shield weakened during the geomagnetic storm which allows interplanetary plasma to penetrate inside the magnetosphere which further affects ionosphere as well as upper atmosphere. Mostly, CMEs generated severe/extreme magnetic storms recovers within one or two days. But, here, we demonstrate a case study of a particular extreme geomagnetic storm caused by CME which depicts a longer recovery phase than usual. The SYM 􀀀 H index lower down to min 􀀀305 nT and recovered to 􀀀165 nT within 2:5 hrs. However, further recovery of the storm suddenly slowed down i.e. ( 0:79 nT hr) and eventually took 4:5 days. This typical feature of recovery is not expected with CME induced storms and further threatened us by various hazardous effects. The present study suggests that the possible causing agent for such extended recovery of the storm is Alfvén wave. The study implies that the Alfvén waves are not only extending the recovery time of weak or moderate storms but also contribute to slow down the recovery of severe/extreme storms.