Superstorm, Supersubstorms, and Joule Heating during the May 2024 event: interplanetary triggers, energy budget, and mechanisms

The May 2024 superstorm (SYM-H peak = –518 nT) was characterized by a three-step main phase, a long and strong recovery phase, and six isolated supersubstorms (SSSs; SML < –2500 nT). We will show that the SSSs were triggered by a strong solar wind driving of ~1017 J. All six SSS events could be explained by both precursor energy and direct driving. The SSS events were unique with highly varied morphology, ranging from an isolated substorm morphology to a storm convection bay scenario. We suggest a two-mode nightside convection electric field to explain the nightside Joule heating variability, and three possible mechanisms for the dayside Joule heating.ReferencesHajra, R., B. T. Tsurutani, G. S. Lakhina, Q. Lu, and A. Du (2024), Interplanetary Causes and Impacts of the 2024 May Superstorm on the Geosphere: An Overview, J. 974, 264 https://doi.org/10.3847/1538-4357/ad7462Hajra, R., B. T. Tsurutani, Q. Lu, A. Du, and G. S. Lakhina (2025), Supersubstorms during the May 2024 superstorm, Space Weather Space Clim. 15, 51 https://doi.org/10.1051/swsc/2025047