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.
