Magnetospheric Response to the Mother’s Day Weekend Geomagnetic Storm: Observations from Geostationary Satellites

The Mother’s Day weekend geomagnetic storm during 10-11 May 2024 is one of the most intense events in recent decades. At least two interplanetary coronal mass ejections (ICMEs) erupted from the active region 13664 on 8 May stacked together, causing the shock observed at the L1 point on 10 May at 17:05 UT. In this study, we utilized geostationary orbit satellite observations to investigate the disturbance of magnetic fields and particles inside the Earth’s magnetosphere. There are four significant findings in this study. First, the subsolar magnetopause had already compressed from about 11.7 R_E (at 13:18 UT) to 8.6 R_E (at 16:59 UT) before the shock arrival, which THEMIS-A observed, then compressed below 6.6 R_E (i.e., geostationary orbit) because of the ICME. Second, Magnetospheric Particle Sensors onboard GOES-16 and GOES-18 detected proton flux increases inside the magnetosphere from about 15:00 UT before the shock arrived. Third, the Energetic Heavy Ion Sensor onboard the GOES-16 and GOES-18 satellites detected helium flux increases on 10 May at about 14:09 and 14:44 UT, respectively. Fourth, the GOES magnetometer recorded the southward magnetic field B_Z on 11 May when the two satellites were in the tail region.