The impact of the May 11th 2024 solar storm on Earth’s environment and atmosphere, combining space borne observations and AtRIS simulations.

On the May 11^th 2024, a succession of CMEs merged in the interplanetary space before striking the Earth. On impact, the interplanetary magnetic field Bz was strongly negative causing an extreme geomagnetic storm, the most intense one seen in the last 20 years. This geomagnetic storm strongly modified fluxes of particles in both the proton and the electron radiation belts. In the case of electrons, this extreme storm led to the direct injection of electrons in the inner belt but also lead to the apparition of multiple electronic belts during the recovery phase. An other implication of this storm was the enhanced electron precipitation flux into the atmosphere. Moreover, solar protons penetrated the magnetosphere causing a Solar Energetic Particle (SEP) event which was measured at geostationary orbit by GOES and in Low Earth Orbit by the EPT. In turn, with those observations and the use of the Atmospheric Radiation Interaction Simulator (AtRIS), the effects of the storm on the atmosphere (ionization and radiation dose rates) are estimated, including the Galactic Cosmic Ray (GCR) Forbush decrease, solar protons and the change in vertical rigidity cutoff. Moreover, observations of atmospheric ozone content from the Aura/MLS instrument show that the event of May 2024 caused a temporary depletion of mesospheric ozone in response to increased ionization rates.