Ionospheric Super Bubbles Near Sunset and Sunrise During the 26-28 February 2023 Geomagnetic Storm

Ionospheric equatorial plasma bubbles (EPBs) are usually generated around sunset over equatorial to low latitudes. In this study, super EPBs extending to middle latitudes were observed, which were freshly generated at both post-sunset and near-sunrise periods over East/Southeast Asia during the geomagnetic storm on 26-28 February 2023. The post-sunset (near-sunrise) EPB persisted similar to 4 (8) hours, drifting eastward (westward) and extending up to similar to 35 degrees N. Strong L-band scintillations, deep total electron content (TEC) depletions and significant positioning errors were caused by the post-sunset EPB. However, the scintillations and TEC depletions linked with the near-sunrise EPB were relatively weaker, and no apparent positioning error was caused. Before the onsets of the post-sunset EPBs, rapid upward vertical plasma drifts of similar to 60 m/s, which could be linked with storm-time prompt penetration electric fields, were observed at magnetic equator. The upward vertical drifts could amplify the F-region bottomside perturbation via increasing the growth rate of Rayleigh-Taylor (R-T) instability and lead to the generation of post-sunset EPBs. On the other hand, before the onset of near-sunrise EPBs, the uplift of F layer was more significant at higher latitudes than that at magnetic equator, probably indicating the presence of equatorward neutral wind. Both the equatorial F layer uplift and equatorward neutral wind could contribute to the growth of R-T instability and favor the generation of near-sunrise EPBs.