Significant Midlatitude Bubble-Like Ionospheric Super-Depletion Structure (BLISS) and Dynamic Variation of Storm-Enhanced Density Plume During the 23 April 2023 Geomagnetic Storm

Abstract

This paper investigates the midlatitude ionospheric disturbances over the American/Atlantic longitude sector during an intense geomagnetic storm on 23 April 2023. The study utilized a combination of ground-based observations (Global Navigation Satellite System total electron content and ionosonde) along with measurements from multiple satellite missions (GOLD, Swarm, Defense Meteorological Satellite Program, and TIMED/GUVI) to analyze storm-time electrodynamics and neutral dynamics. We found that the storm main phase was characterized by distinct midlatitude ionospheric density gradient structures as follows: (a) In the European-Atlantic longitude sector, a significant midlatitude bubble-like ionospheric super-depletion structure (BLISS) was observed after sunset. This BLISS appeared as a low-density channel extending poleward/westward and reached ∼40° geomagnetic latitude, corresponding to an APEX height of ∼5,000 km. (b) Coincident with the BLISS, a dynamic storm-enhanced density plume rapidly formed and decayed at local afternoon in the North American sector, with the plume intensity being doubled and halved in just a few hours. (c) The simultaneous occurrence of these strong yet opposite midlatitude gradient structures could be mainly attributed to common key drivers of prompt penetration electric fields and subauroral polarization stream electric fields. This shed light on the important role of storm-time electrodynamic processes in shaping global ionospheric disturbances.Plain Language SummaryThe storm-time midlatitude ionosphere is a highly dynamic region that can exhibit much more pronounced electron density gradients and disturbances than expected. The combined data from ground-based and satellite measurements provided valuable insights into the intricate behavior of the midlatitude ionosphere during an intense geomagnetic storm on 23 April 2023. The midlatitude ionosphere was characterized by significant electron density gradient structures, comprising both phenomenal density depletion and exceptional enhancements. Notably, a remarkable band-like ionospheric super-depletion structure was observed in local dusk, which extended to ∼40° geomagnetic latitude, corresponding to an altitude of ∼5,000 km above the geomagnetic equator. In contrast, a significant midlatitude ionospheric density enhancement plume appeared simultaneously in local afternoon, which exhibited a dynamic variation with its intensity being quickly doubled and halved in just a few hours. The synchronous occurrence of these striking yet opposing density gradients highlights the importance of electrodynamic effect driven by common key drivers of storm-time perturbed electric fields. This underscores the complex and interconnected nature of the ionospheric response during intense geomagnetic storms.Key PointsThe storm main phase was characterized by coincident nightside bubble-like ionospheric super-depletion structure (BLISS) and dayside storm-enhanced density (SED)The BLISS manifested as a poleward/westward-streaming channel and extended to ∼40 MLAT, corresponding to an APEX height of ∼5,000 kmThe SED plume experienced a dynamic variation with the plume intensity being quickly doubled and halved in just a few hours