Ozone decrease observed in the upper atmosphere following the May 11th 2024 Mother's Day and the June 8th solar storms.

On May 11th 2024, a succession of coronal mass ejections that merged together struck the Earth and induced large
scale perturbations in the magnetosphere. During this event, satellite observations showed a large solar energetic proton (SEP)
event associated to an extreme geomagnetic storm. At the same time, satellite observations of atmospheric ozone have been
performed by AURA/MLS. In this work, we present the first observations of the effect of the storm of May and the following
SEP of June 8th on ozone concentration throughout the atmosphere. Observations of the MLS show that the event of May lead
to stronger depletion of O3 in the upper part of the atmosphere than in June. This difference is explained by the type of particle
precipitation that occurred during the two events, with both protons and electrons in May and only protons in June. Neither
event caused ozone depletion in the stratosphere while strong decreases are observed in the mesosphere. In May, mesospheric
ozone depletion is observed during 18 days and reaches a maximum of 60%. In addition, the storm of May also caused a
noticeable decrease in ozone concentration (up to 20%) at altitudes above 90 km.