The Role of an Alfvén wave in an extended recovery phase of an ICME induced extreme geomagnetic storm   

Komal Choraghe - Department of Physics, University Of Mumbai 

Session: QV - Earth's Magnetosphere and Radiation Belts

Abstract

Geomagnetic storms are crucial phenomena during 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
is weakened during a geomagnetic storm, which allows interplanetary plasma to penetrate inside the magnetosphere, further affecting the ionosphere as well as the upper atmosphere. Mostly, CMEs generating severe/extreme magnetic storms recover within one or two days. However, here, we demonstrate a case study of a particular extreme geomagnetic storm (SYM-H= -305 nT) caused by a CME that exhibits a longer recovery phase than usual. Our study suggests that the possible causal agent for such extended recovery of the storm is the Alfvén wave. We further study recovery phases of 12 extreme geomagnetic storms. We observed distinct two trends i.e. fast and slow recovery phase for each storm. Based on this we tried to understand the relationship between storms recovery phases and exponential decay function, hyperbolic decay function and constant decay function.