Abstract:
We investigate the role of storm time electrodynamics in suppressing the equatorial plasma
bubble (EPB) development using multi-instruments over India during a moderate geomagnetic storm that
occurred on 2 October 2013 where Dst minimum reached ~ 80 nT. This storm produced unique signatures
in the equatorial ionosphere such that equatorial electrojet strength showed signatures of an abrupt increase
of its strength to 150 nT and occurrence of episodes of counter electrojet events. During the main phase
of the storm, the interplanetary magnetic field Bz is well correlated with the variations in the equatorial
electrojet/counter electrojet suggesting the role of undershielding/overshielding electric fields of
magnetospheric origin. Further, observations showed the presence of strong F3 layers at multiple times at
multiple stations due to undershielding electric field. Interestingly, we observed simultaneous presence of F3
layers and suppression of EPBs in the dusk sector during the recovery phase. While strong EPBs were
observed before and after the day of the geomagnetic storm, suppression of the EPBs on the storm day
during “spread F season” is intriguing. Our further analysis using low-latitude station, Hyderabad, during the
time of prereversal enhancement suggests that intense Esb layers were observed on the storm day but were
absent/weak on quiet days. Based on these results, we suggest that the altitude/latitude variation of
disturbance dynamo electric fields/disturbance winds may be responsible for simultaneous detection of F3
layers, occurrence of low-latitude Es layers, and suppression of EPBs during the storm day along the
sunset terminator.
