GOES Plasma Observations Applied to the Magnetospheric Boundary Study

Geostationary Operational Environmental Satellites (GOES) in geostationary orbit (GEO) have previously been utilized for magnetospheric studies using magnetic field data; however, plasma measurements from GOES have received little attention. Since GOES-16, the onboard Magnetospheric Particle Sensors - Low Energy instrument has allowed measurements of ions and electrons in the range from ~30 eV to 30 keV. During extreme solar wind conditions, boundary layers, dayside magnetopause, and even the bow shock may be compressed to GEO, making plasma measurements from GOES valuable for providing energy flux spectra, pitch-angle distributions, and plasma moments at this position, as well as for conjunction observations with other missions. In this study, we present coordinated GOES and THEMIS observations during the 10 May 2024 solar wind event. The energy flux data for both missions are shown. We identify a new structure on the inner side of the magnetopause, which we term a “compression layer”, within which a “three-energy-level” structure is observed. We suggest that both structures are related to pure compression under northward IMF and the plasmaspheric plume. We also show that the bow shock was temporarily compressed to GEO during this event, and we further present additional examples illustrating the application of GOES plasma observations to magnetospheric boundary studies.