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1. An Extreme Auroral Electrojet Spike During 2023 April 24th Storm

   https://doi.org/10.1029/2023AV001101  

   Zou, Ying; Gjerloev, Jesper_W; Ohtani, Shin; Friel, Matt; Liang, Jun; Lyons, Larry_L; Shen, Yangyang; Liu, Jiang; Chen, Li‐Jen; Ferdousi, Banafsheh; et al (April 2024, AGU Advances)

   Abstract Abrupt variations of auroral electrojets can induce geomagnetically induced currents, and the ability to model and forecast them is a pressing goal of space weather research. We report an auroral electrojet spike event that is extreme in magnitude, explosive in nature, and global in spatial extent that occurred on 24 April 2023. The event serves as a fundamental test of our understanding of the response of the geospace system to solar wind dynamics. Our results illustrate new and important characteristics that are drastically different from existing knowledge. Most important findings include (a) the event was only of ∼5‐min duration and was limited to a narrow (2°–3°) band of diffuse aurora; (b) the longitudinal span covered the entire nightside sector, possibly extending to the dayside; (c) the trigger seems to be a transient solar wind dynamic pressure pulse. In comparison, substorms usually last 1–2 hr and span almost the entire latitudinal width of the auroral oval. Magnetic perturbation events (MPEs) span hundreds km in radius. Both substorms and MPEs are mainly driven by disturbances in the magnetotail. A possible explanation is that the pressure pulse compresses the magnetosphere and enhances diffuse precipitation of electrons and protons from the inner plasma sheet, which elevates the ionospheric conductivity and intensifies the auroral electrojet. Therefore, the event exhibits a potentially new type of geomagnetic disturbance and highlights a solar wind driver that is enormously influential in driving extreme space weather events. 

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2. Inferring Zonal Wind Profiles in the Equatorial Electrojet From Coherent Scatter

   https://doi.org/10.46620/22-0019  

   Hysell, D. L.; Chau, J. L.; Conte, J. F.; Flores, R.; Milla, M. A. (January 2022, URSI Radio Science Letters)
3. Quantifying the ability of magnetohydrodynamic models to reproduce observed Birkeland current and auroral electrojet magnitudes

   https://doi.org/10.3389/fspas.2023.1212735  

   James, Tre’Shunda; Lopez, Ramon E; Glocer, Alex (August 2023, Frontiers in Astronomy and Space Sciences)

   Although global magnetohydrodynamic (MHD) models have increased in sophistication and are now at the forefront of modeling Space Weather, there is still no clear understanding of how well these models replicate the observed ionospheric current systems. Without a full understanding and treatment of the ionospheric current systems, global models will have significant shortcomings that will limit their use. In this study we focus on reproducing observed seasonal interhemispheric asymmetry in ionospheric currents using the Space Weather Modeling Framework (SWMF). We find that SWMF does reproduce the linear relationship between the electrojets and the FACs, despite the underestimation of the currents’ magnitudes. Quantitatively, we find that at best SWMF is only capturing approximately 60% of the observed current. We also investigate how varying F10.7 effects the ionospheric potential and currents during the summer and winter. We find that simulations ran with higher F10.7 result in lower ionospheric potentials. Additionally, we find that the models do not always replicate the expected behavior of the currents with varying F10.7. This work points to a needed improvement in ionospheric conductance models. 

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4. Are Supersubstorms Substorms? Extreme Nightside Auroral Electrojet Activities During the May 2024 Geomagnetic Storm

   https://doi.org/10.1029/2024JA033303  

   Zou, Ying; Shin, Ohtani; Gjerloev, Jesper_W; Anderson, Brian_J; Waters, Colin_L; Wang, Chih‐Ping; Liang, Jun; Lyons, Larry_L; Bhatt, Asti (March 2025, Journal of Geophysical Research: Space Physics)

   Abstract Enhancement of currents in Earth's ionosphere adversely impacts systems and technologies, and one example of extreme enhancement is supersubstorms. Despite the name, whether a supersubstorm is a substorm remains an open question, because studies suggest that unlike substorms, supersubstorms sometimes affect all local times including the dayside. The spectacular May 2024 storm contains signatures of two supersubstorms that occurred successively in time with similar magnitude and duration, and we explore the nature of them by examining the morphology of the auroral electrojet, the corresponding disturbances in the magnetosphere, and the solar wind driving conditions. The results show that the two events exhibit distinctly different features. The first event was characterized by a locally intensified electrojet followed by a rapid expansion in latitude and local time. Auroral observations showed poleward expansion of auroras (or aurorae), and geosynchronous observations showed thickening of the plasma sheet, magnetic field dipolarization, and energetic particle injections. The second event was characterized by an instantaneous intensification of the electrojet over broad latitude and local time. Auroras did not expand but brightened simultaneously across the sky. Radar and LEO observations showed enhancement of the ionospheric electric field. Therefore, the first event is a substorm, whereas the second event is enhancement of general magnetospheric convection driven by a solar wind pressure increase. These results illustrate that the so‐called supersubstorms have more than one type of driver, and that internal instability in the magnetotail and external driving of the solar wind are equally important in driving extreme auroral electrojet activity. 

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5. Counter‐Electrojet Occurrence as Observed From C/NOFS Satellite and Ground‐Based Magnetometer Data Over the African and American Sectors

   https://doi.org/10.1029/2019SW002236  

   Habarulema, John Bosco; Lefebvre, Gabrielle; Moldwin, Mark B.; Katamzi‐Joseph, Zama T; Yizengaw, Endawoke (July 2019, Space Weather)

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