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Abstract We study the impact of the evolving magnetosphere‐ionosphere‐thermosphere system on upward ion fluxes during the 23–24 April 2023 geomagnetic storm. This storm has a “double‐dip” structure where two southward IMF periods cause two dips in the SYM‐H index. The auroral electrojet indices and field‐aligned currents reveal comparable ionospheric energy inputs during both dips. We use global total electron content maps to track mid‐to‐high‐latitude ionospheric density structures, which are known to have significant effects on upward ion fluxes. We find that each southward turning triggers a positive ionospheric storm phase. However, thermospheric O/N2depletions initiated during the 1st dip moderate the effects of magnetospheric driving on the ionosphere during the 2nd dip. Consequently, the density structures in the second positive phase are weaker and confined to lower latitudes than before. We use density and velocity measurements from DMSP satellites to identify regions with strong upward ion fluxes. We find that the storm‐enhanced density (SED) plume from the 1st dip drives significant upward fluxes when it crosses the open‐closed field line boundary. Comparable fluxes exist in the dawn sector due to large upward drifts driven by persistent energy inputs under strong negative conditions. We conclude that the evolution of storm‐time ion upflow flux has a local time dependency. The density‐regulated afternoon/evening sector fluxes are seeded by ionospheric high‐density structures and modulated by the thermospheric composition, while the velocity‐regulated dawn/morning sector fluxes are more consistent throughout the storm due to the steady magnetospheric driving under strong negative conditions.
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Responses of Field‐Aligned Currents and Equatorial Electrojet to Sudden Decrease of Solar Wind Dynamic Pressure During the March 2023 Geomagnetic Storm
Abstract We present the observations of field‐aligned currents and the equatorial electrojet during the 23 March 2023 magnetic storm, focusing on the effect of the drastic decrease of the solar wind dynamic pressure occurred during the main phase. Our observations show that the negative pressure pulse had significant impact to the magnetosphere‐ionosphere system. It weakened large‐scale field‐aligned currents and paused the progression of the storm main phase for ∼3 hr. Due to the sudden decrease of the plasma convection after the negative pressure pulse, the low‐latitude ionosphere was over‐shielded and experienced a brief period of westward penetration electric field, which reversed the direction of the equatorial electrojet. The counter electrojet was observed both in space and on the ground. A transient, localized enhancement of downward field‐aligned current was observed near dawn, consistent with the mechanism for transmitting MHD disturbances from magnetosphere to the ionosphere after the negative pressure pulse.
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- PAR ID:
- 10515569
- Publisher / Repository:
- American Geophysical union
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 51
- Issue:
- 10
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024GL109427
