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

Abstract

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 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 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/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 non-homogeneities 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 non-trivial evolution of the shock parameters during its journey through the interplanetary space.

Figures (12)

• Figure 1: Spacecraft locations in HEEQ coordinate system on 2023 March 13 at 03:45 UT. The shaded area represents the eruption sector associated to the primary propagation direction.
• Figure 2: Total brightness of base difference images taken on 2023 March 13 at 03:53 UT (a), 04:23 UT (b) and 04:38 (c) from STEREO-A/COR2. In panel (b) dashed lines refer to the shock front (red curve) and flux rope (blue line). The threshold intensity has been chosen with the minimum value equal to zero, in order to darken the background and to highlight the presence of the shock in front of the CME.
• Figure 3: Magnetic field and plasma observations by PSP (a), SolO (b), STEREO-A (c), and Wind (d). From top to bottom, the panels show the magnetic field components and magnitude, the bulk velocity components and magnitude, the proton density and the plasma temperature. The vertical dashed lines indicate the time of the spacecraft shock crossings, PSP on 13 March at 07:13 UT, SolO on 14 March at 01:08 UT, STEREO-A on 15 March at 01:16 UT, and Wind on 15 March at 04:02 UT, respectively. The shaded areas mark the time interval in the upstream and downstream regions to calculate the shock parameters.
• Figure 4: Quasi simultaneous observations of the CME on 2023 March 13 by STEREO-A/COR2 at 04:23 UT and SoHO/C3 at 04:18 UT. Blue curves represent the shock front modeled with the ellipsoid model. The images have been adapted from the "CGS in Python" tool, available at https://github.com/johan12345/gcs_python.
• Figure 5: Sketch of the shock density profile as a function of the distance $s$ along the shock normal. The upstream and downstream widths of the profiles $(d_u,d_d)$, as well as the position of the shock front $s^\star$ are shown. We also indicate the position of the shock front $s_{sh}$ determined from the geometric modeling, and the shift $\Delta_s$, which is used to correct the location of the front based on the analysis of the brightness profiles (see text for further details).