Context: The geomagnetic storm of 10–11 May 2024, also known as the Mother's Day storm or Gannon storm, was among the most intense geomagnetic storms in recent decades. Such storms are associated with hazards, including induced currents in power grids, caused by intense ionospheric currents associated with auroral processes. Since the equatorward expansion of the auroral oval is related to the intensity of the storm, such intense events can affect infrastructures that are seldom exposed to such hazards. The May 2024 storm was the first event of this intensity in two decades, and therefore the first that can be studied with our current observational capabilities. Aim: The expansion of the auroral oval was observed by the FRIPON all-sky camera network, originally designed to detect fireballs. With over 150 cameras deployed globally, the network provides a valuable opportunity to map the evolution of the auroral oval's expansion at relatively low latitudes during the night. In addition, several Low Earth Orbiting satellites with capabilities to observe auroral processes passed over Europe during the night of the storm, allowing us to compare their observations. Methods: In a proof-of-concept approach, we analyse the evolution of the brightness intensity at zenith for each FRIPON camera in Europe. This simple technique enables the tracking of the Southern limit of the visible aurorae over time. The results are compared with ground magnetometer measurements, optical satellite remote-sensing observations of auroral emissions, field-aligned currents from magnetometers on the Swarm satellites and enhancements in ionospheric Total Electron Content (TEC) obtained from Global Navigation Satellite System (GNSS) receiver networks. Results: We observe that the aurorae extend as far south as 46^~N geographic (42^~N Quasi-Dipole geomagnetic latitude), a significantly lower position than predicted by some models. In addition to this observation, a faint increase in luminosity was detected over the zenith for a large majority of cameras across Southern Europe witnessing a Stable Aurora Red (SAR) Arc, spanning from 37^ to 50^ in latitude. Conclusions: This work validates the use of the FRIPON network (or other similar networks) for Spacer Weather research. Complementary to other Spacer Weather instruments, it may help in studying the dynamics of the auroral oval.
Katz et al. (Sun,) studied this question.