Compression of Earth's Magnetopause Down to 5 R_E During the Superstorm on 10 May 2024

On 10 May 2024, a super space storm—characterized by the Dst index plummeting to −412 nT and induced by a strong coronal mass ejection on the Sun—attacked the Earth's magnetosphere. This geomagnetic storm, according to the human record of Dst index, is the third-strongest one throughout history (only slightly lower than those in 1989 and 2003). In such an extreme condition, how the magnetopause evolves and reforms remains unclear, because only a few spacecraft measurements were available in the dayside magnetosphere during previous events. Here, by utilizing in-situ measurements of multiple spacecraft together with ground magnetometers, we for the first time determine the extreme compression of the magnetopause from higher than 10 R_E down to 5 R_E. This observation of such severe deformation is also consistent with the prediction of the theoretical model. This study provides crucial insights into the extreme behavior of the magnetopause during the influence of a superstorm.