An Extreme Auroral Electrojet Spike During 2023 April 24th Storm

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 similar to 5-min duration and was limited to a narrow (2 degrees-3 degrees) 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. Auroral electrojets are horizontal electric currents that flow in the auroral ionosphere, and extreme auroral electrojet activities can induce geomagnetically induced currents that damage high-voltage power transformers and increase steel corrosion of pipeline networks. Understanding what drives the extreme events is therefore 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. Most important findings include (a) the event was only of similar to 5-min duration and was limited to a narrow band of diffuse aurora; (b) the longitudinal span covered the entire nightside sector; (c) the trigger seems to be a transient solar wind dynamic pressure pulse. These features differ drastically from other widely known geomagnetic disturbances such as substorms or magnetic perturbation events, and signify a potentially new type of disturbance. A possible explanation is that the solar wind pressure pulse compresses the magnetosphere, enhances diffuse precipitation of particles into the ionosphere, and elevates the ionospheric conductivity. An abrupt and intense auroral electrojet enhancement occurred during the storm of 24 April 2023 This extreme event differs from typical geomagnetic disturbances in terms of magnitude, spatiotemporal extent, and physical driver The event was triggered by a solar wind pressure pulse, which enhanced diffuse auroral precipitation and ionospheric conductivity