Joint investigation of the September 5, 2022, coronal mass ejection event with remote observations, numerical simulations, and in situ measurements

A very fast coronal mass ejection (CME) was ejected on September 5, 2022, which was measured in situ by Parker Solar Probe (PSP) and Solar Orbiter, and observed remotely by Stereo-A, SOHO and PSP. Here, we carry out the reconstruction of the CME in the corona by using SOHO/LASCO, STEREO-A/COR2, and PSP/WISPR data. The obtained CME parameters are used as input for an MHD simulation with the PLUTO code of an erupting flux rope propagating into the Parker spiral reconstructed with RIMAP, a method which reconstructs the heliosphere on the ecliptic plane from in situ measurements acquired by spacecraft with heliocentric orbits. Then we analyze in-situ Solar Orbiter measurements at 0.7 AU to check the results of the RIMAP simulation, to study the CME-driven shock properties and how they compare with the simulated ones. The level of magnetic turbulence around the shock and the transport of energetic particles are also considered: large fluxes of energetic particles accelerated in situ are measureded by Solar Orbiter/EPD instrument in the energy range 111 keV-3.7 MeV, causing an amplification of magnetic fluctuations. Analyzing the upstream energetic particle time profiles, the transport regime of accelerated particles is found to be normal, although non Gaussian features are also present. As a surprising results, we find that the energetic particles differential flux at Solar Orbiter has a spectral index harder than that predicted by diffusive shock acceleration for the measured compression ratio. The possible reasons for such a discrepancy are discussed.