Three-dimensional monitoring of Ionospheric storms using COSMIC-2 RO

High-rate Radio Occultation (RO) measurement using the COSMIC-2 constellation has enabled the observation of the transient changes in the ionosphere's three-dimensional (3D) structure.  This capability enables studying the changes to the 3D ionospheric structure during a geomagnetic storm. So far, the ionospheric storms (positive/negative ionospheric storms) that follow space weather events, have mostly been studied globally using two-dimensional (2D) TEC maps generated using ground-based networks. Ground-based networks also limit the measurements to only over the landmass and islands. High-rate 3D observation from COSMIC-2 can overcome these limitations of the ground-based networks. Such measurements provide 3D ionospheric variations over a large region lying within +/- 40⁰ geographic latitude, with a spatiotemporal resolution significant enough to provide new insights.  This paper presents a 3D perspective of the ionospheric impact of the November 04, 2021, geomagnetic storm. In the present study, electron density has been binned with latitude, longitude, altitude, and time resolution of 6⁰, 30⁰, 25 km, and 2 hours, respectively. It must be noted that the present study excludes electron density variation below 225 km altitude where RO retrievals are not considered reliable. Some of the key observed features of the ionospheric storm under consideration are: (a) Large enhancement in the ionospheric plasma density due to the enhanced ‘fountain effect’ in the main phase is most significant in the topside ionosphere with a maximum variation observed above 450 km, (b) the most significant enhancement in the topside ionospheric plasma density (positive storm effect) was seen during the midnight period, irrespective of the longitude under consideration, (c) enhancement in the electron density also indicated some longitudinal dependence, and (d) most significant impact of the ionospheric storm was observed over the latitudinal belt lying beyond the poleward boundary of the EIA crests.  These and several other interesting observations will be presented. Results will also be discussed in light of the current understanding of ionospheric storms.