On the Mesoscale Structure of Coronal Mass Ejections at Mercury’s Orbit: BepiColombo and Parker Solar Probe Observations

Abstract

On 2022 February 15, an impressive filament eruption was observed off the solar eastern limb from three remote-sensing viewpoints, namely, Earth, STEREO-A, and Solar Orbiter. In addition to representing the most-distant observed filament at extreme ultraviolet wavelengths—captured by Solar Orbiter's field of view extending to above 6 R ⊙—this event was also associated with the release of a fast (∼2200 km s−1) coronal mass ejection (CME) that was directed toward BepiColombo and Parker Solar Probe. These two probes were separated by 2° in latitude, 4° in longitude, and 0.03 au in radial distance around the time of the CME-driven shock arrival in situ. The relative proximity of the two probes to each other and the Sun (∼0.35 au) allows us to study the mesoscale structure of CMEs at Mercury's orbit for the first time. We analyze similarities and differences in the main CME-related structures measured at the two locations, namely, the interplanetary shock, the sheath region, and the magnetic ejecta. We find that, despite the separation between the two spacecraft being well within the typical uncertainties associated with determination of CME geometric parameters from remote-sensing observations, the two sets of in situ measurements display some profound differences that make understanding the overall 3D CME structure particularly challenging. Finally, we discuss our findings within the context of space weather at Mercury's distance and in terms of the need to investigate solar transients via spacecraft constellations with small separations, which has been gaining significant attention during recent years.

A Coronal Mass Ejection Impacting Parker Solar Probe at 14 Solar Radii

“…The discontinuity observed around 14:00 is followed by an approximately 30-minute period of decreased magnetic field intensity and increased density. This behavior resembles heliospheric plasma sheet regions identified in previous PSP studies (Lavraud et al 2020;Palmerio et al 2024). We also identified a magnetic field reversal at 17:30 UT, which we interpret as a heliospheric current sheet crossing.…”

Persistent Behavior in Solar Energetic Particle Time Series

“…Period A has a 10 day duration starting from 2023 September 22, 00:01 UTC, and corresponds to an active-Sun interval. Period B has a 5 day duration starting from 2022 February 15, 12:00 UTC, during which PSP encountered a fast (2300 km s -1 ) coronal mass ejection (CME; Khoo et al 2024;Palmerio et al 2024). Finally, a 5 day period starting on 2021 April 23, 00:00 UTC, offers an example of the quiet Sun and constitutes period C. We focus on the H + measurements consisting of the energy channels in the range of 80-2000 keV (see, e.g., Figure 2).…”

A Survey of Coronal Mass Ejections Measured In Situ by Parker Solar Probe during 2018–2022

“…However, such multispacecraft encounters also depend on fortuitous radial and longitudinal lineups of space probes. Also, factors such as inclination (e.g., Kilpua et al 2009;Davies et al 2021b), longitudinal separation (e.g., Farrugia et al 2011;Kilpua et al 2011;Winslow et al 2015;Lugaz et al 2018;Mishra et al 2021;Pal et al 2023;Palmerio et al 2024), interactions with other structures (e.g., Möstl et al 2012;Prise et al 2015;Winslow et al 2016Winslow et al , 2021Lugaz et al 2022), and physical effects such as erosion, deformation, and distortion (e.g., Ruffenach et al 2012;Wang et al 2018;Palmerio et al 2021;Weiss et al 2021) can induce fundamental changes in ICME measurements from one spacecraft to another and limit the generality of the findings. Another intrinsic drawback of most of the previous statistical approaches has been examining ICME evolution with clusters of in situ measurements at certain locations rather than a more continuous coverage.…”