Abstract:
Recurrent high speed solar wind streams from coronal holes on the Sun are more frequent and Geoeffective during the declining phase of solar cycle which interact with the ambient solar wind leading the formation of Corotating Interaction Regions (CIRs) in the interplanetary medium. These CIR-High Speed Stream (HSS) structures of enhanced density and magnetic fields, when they impinge up on the Earth’s magnetosphere, can cause recurrent geomagnetic storms in the Geospace environment. In this study, we investigate the influence of two CIR-driven recurrent geomagnetic storms on the equatorial and low-latitude ionosphere in the context of the development of equatorial plasma bubbles over Indian and Asian longitudes. The results consistently indicate that prompt penetration of eastward electric fields into equatorial and low-latitudes under southward IMF Bz can occur even during the CIR-driven storms. Further, the penetration of eastward electric fields augments the evening pre-reversal enhancement and triggers the development of EPBs over wide longitudinal sectors where the local post-sunset hours coincide with the main phase of the storm. Similar results that are consistently observed during both the CIR-driven geomagnetic storms are reported and discussed in this paper.
