On the mesoscale structure of CMEs at Mercury's orbit: Parker Solar Probe and BepiColombo observations

<p>On 15 February 2022, an impressive filament eruption was observed off the solar eastern limb from three remote-sensing viewpoints, namely Earth, STEREO-A, and Solar Orbiter. Apart from representing the most-distant observed filament at extreme ultraviolet wavelengths&#8212;captured by Solar Orbiter's field of view extending to above 6 Rs&#8212;this event was also associated with the release of a fast (~2200 km/s) coronal mass ejection (CME) that was directed towards Parker Solar Probe and BepiColombo.</p> <p>Parker Solar Probe and BepiColombo were separated by 3&#176; in latitude, 4&#176; in longitude, and 0.03 au in radial distance at the time of the CME-driven shock arrival at the two spacecraft. The relative proximity of the two probes to each other and to the Sun (~0.365 au) allows us to study the mesoscale structure of CMEs at Mercury's orbit for the first time. We analyse similarities and differences in the magnetic structure of the CME ejecta measured at the two locations, as well as other properties such as shock/sheath characteristics, pitch-angle distributions, and impact of the interaction between the ejecta and its surroundings. Finally, we contextualise our findings within the current discussions on the need to investigate solar transients via spacecraft constellations with small separations, which have been gaining significant attention during recent years.</p>