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

Abstract

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 ∼4 (8) hours, drifting eastward (westward) and extending up to ∼35°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 ∼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.

Multi-Instrument Observation of the Ionospheric Irregularities and Disturbances during the 23–24 March 2023 Geomagnetic Storm

“…Recent studies have incorporated multi-instrument observations to analyze the ionospheric irregularities induced by geomagnetic storms. The use of ground-and space-based observables can cross-validate the results from various atmospheric layers [13,21,32]. In addition, electron density measurements of F-layer, assimilation of magnetometer data, satellite-derived thermospheric O/N 2 and the neutral wind observations from Fabry-Perot interferometers (FPIs) have enabled to study the ionospheric-thermospheric coupling in detail [33,34].…”

“…Abdu [12] reported that the growth rate of R-T instability is enhanced/decreased due to the variations in equatorial E region electric fields during different phases of the geomagnetic storms. The enhanced pre-sunset eastward electric fields play a major role in the uplifting of ionospheric plasma, instigating (increasing ionospheric heights, hmF2) the formation of post-sunset equatorial plasma bubbles (EPBs) reaching up to higher latitudes ( [13], and references therein). Although, during the high solar activity periods and equinox season, post-sunset EPBs are common in the American and Asian sectors [14][15][16], nevertheless, the irregularity is confined to equatorial latitudes under normal conditions [13].…”

“…The enhanced pre-sunset eastward electric fields play a major role in the uplifting of ionospheric plasma, instigating (increasing ionospheric heights, hmF2) the formation of post-sunset equatorial plasma bubbles (EPBs) reaching up to higher latitudes ( [13], and references therein). Although, during the high solar activity periods and equinox season, post-sunset EPBs are common in the American and Asian sectors [14][15][16], nevertheless, the irregularity is confined to equatorial latitudes under normal conditions [13]. Similarly, the post-sunset irregularities can be suppressed or inhibited during the geomagnetic storms owing to the westward PPEF and DDEF acting at night and daytime, respectively [12,17].…”

“…Similarly, the post-sunset irregularities can be suppressed or inhibited during the geomagnetic storms owing to the westward PPEF and DDEF acting at night and daytime, respectively [12,17]. Moreover, the formation of post-midnight or near-sunrise equatorial spread-F (ESF) or EPBs during geomagnetic storms is not common [13]. Several studies suggested that the EPBs observed at dawn or post-sunrise periods are the remnant of post-sunset EPBs [18][19][20].…”

“…The cycle slip and loss-of-lock to the Global Navigation Satellite System (GNSS) severely affect the positioning and navigation services (ref. [13], and references therein).…”