Evolution of the Shock Properties of the 2023 March 13 Event from In Situ and Remote-sensing Data

Shocks driven by coronal mass ejections (CMEs) are the most powerful accelerators of gradual solar energetic particles (SEPs) in the inner heliosphere. On 2023 March 13, a halo CME, as seen from the Solar and Heliospheric Observatory (SOHO) and the Sun TErrestrial Relations Observatory (STEREO), gave rise to a strong SEP event. In this work, we aim to analyze this CME-driven shock from multiple spacecraft, using both remote-sensing observations from STEREO-A/COR2 and in situ data from the Parker Solar Probe (PSP), Solar Orbiter (SolO), and Wind. In order to determine its direction of propagation and kinematic properties, we model the shock geometry using STEREO-A/COR2 and SOHO Large Angle and Spectrometer Coronagraph (LASCO)/C3 observations as an expanding ellipsoid. The density compression ratio of the shock is determined by fitting the brightness profile from the coronagraphic images with that obtained from raytracing simulations of a double-Gaussian shock-density profile. We compare physical quantities such as compression ratio and Alfvénic Mach number derived from remote-sensing observations with in situ measurements by PSP, SolO, STEREO-A, and Wind. From STEREO-A/COR2, we determine the compression ratio around the entire shock front in the corona, finding significant inhomogeneities that can impact the values found during in situ crossings. Following the evolution of the parameters characterizing the CME from the source to space, we find that closer to the Sun both the gas compression ratio and the Alfvénic Mach number remain almost constant, while they increase at larger radial distances. This indicates a nontrivial evolution of the shock parameters during its journey through the interplanetary space.