Impact of Sudden Stratospheric Warming Events on Ionospheric F 2 Region at Low Mid‐Latitude Indian Station, New Delhi

Abstract We investigated the effects of both major and minor Arctic sudden stratospheric warming (SSW) events from 2017 to 2020, along with the 2019 Antarctic SSW, on the ionospheric F2 region using Digisonde observations from a low‐mid latitude Indian station located in New Delhi (28.6°N, 77.2°E; geomagnetic latitude 19.2°N, dip latitude 42.4°N). Our study revealed significant ionospheric changes, with electron densities exhibiting variations of more than 245% during these warming events. We therefore investigated the extent of ionospheric changes following the 2017 and 2018 SSW events using ionosonde data for the first 6 months, revealing that the SSW period showed the highest deviation from median values, highlighting its significant impact on the variability of the ionospheric F2 region. In addition to short‐term oscillations and a distinct 9‐day periodicity, 19–25‐day periodicities are also observed in the F2 layer frequency during the 2017–2020 SSW events, indicating persistent secondary planetary wave modulations consistent with previously reported results. However, our observations did not indicate a lunar influence (14‐day periodicity) in the ionosphere during these events. The Equatorial Electrojet (EEJ) exhibited significant fluctuations at the far equatorial station at New Delhi during the 2017 and 2018 SSW events, resulting in the occurrence of Counter Electrojet (CEJ) phenomena.