Role of the phase of Quasi-Biennial Oscillation in modulating the influence of SSW on Equatorial Ionosphere

Understanding the coupling of ionosphere-thermosphere (IT) system from the lower atmospheric forcing is one of the primary challenges for the space weather community. The present paper deals with the role of two lower atmospheric processes over the Indian region ionosphere i.e., stratospheric Quasi-Biennial Oscillation (QBO) and Sudden Stratospheric Warming (SSW). The role of QBO in modulating the response of equatorial/low latitude ionosphere over Indian sector to the major SSW events of 2009 and 2013 has been investigated by using combined measurements from meteor wind radar operating over Trivandrum, Global Positioning System (GPS) derived total electron content (TEC), and magnetic field data. The time variation of Equatorial Electrojet (EEJ)-induced surface magnetic field show that the response of EEJ is distinctly different during different phases of the QBO. The peaking time of EEJ and occurrence time of counter electrojet (CEJ) were found to be shifted towards morning/evening sector during the westward/eastward phase of the QBO during the SSW years. The TEC over both the equatorial and low-latitude ionosphere exhibit a similar feature. The tidal components derived from horizontal winds using a meteor wind radar revealed similar shift in their peaking time. These observations clearly vindicate that the phase of QBO plays a crucial role in structuring the equatorial electrodynamics and electron density distribution over low-latitudes during the SSW evens. These results are unique and achieves significance as we are heading towards solar minimum period where forcing from the lower atmosphere is an import aspect of ionospheric variability.