Internal magnetic field structures observed by PSP/WISPR in a filament-related coronal mass ejection^⋆

¹ Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
e-mail: greta.cappello@uni-graz.at
² The Johns Hopkins University Applied Physics Laboratory, 11101 Johns Hopkins Road, Laurel, MD 20723, USA
³ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
⁴ Department of Physics, Montana State University, Bozeman, MT 59717, USA
⁵ Kanzelhöhe Observatory for Solar and Environmental Research, University of Graz, 9521 Treffen, Austria
⁶ Institut für Astrophysik und Geophysik, Georg-August-Universität, Göttingen, Germany

Received: 14 February 2024
Accepted: 24 April 2024

Abstract

Context. We investigated the coronal mass ejection (CME) related to an eruptive filament over the southwestern solar limb on December 8, 2022, at around 8 UT. We tracked localized density enhancements reflecting the magnetic structures using white-light data taken with the Wide-field Instrument for Solar PRobe (WISPR) aboard the Parker Solar Probe (PSP).

Aims. We aim to investigate the 3D location, morphology and evolution of the internal magnetic fine structures of CMEs. Specifically, we focused on the physical origin of the features in the WISPR images, how the white-light structures evolve over time, and their relationship with the source region, filament, and the flux rope.

Methods. The fast tangential motion of the PSP spacecraft during its perihelion permits a single event to be viewed from multiple angles in short times relative to the event’s evolution. Hence, three-dimensional information of selected CME features can be derived from this single spacecraft using triangulation techniques.

Results. We grouped small-scale structures with roughly similar speeds, longitude, and latitude into three distinct morphological groups. We found twisted magnetic field patterns close to the eastern leg of the CME that may be related to “horns” outlining the edges of the flux-rope cavity. We identified aligned thread-like bundles close to the western leg, and they may be related to confined density enhancements evolving during the filament eruption. High density blob-like features (magnetic islands) are widely spread in longitude (∼40°) close to the flanks and the rear part of the CME. We also note that the large-scale outer envelope of the CME, seen clearly from 1 AU, was not well observed by PSP.

Conclusions. We demonstrate that CME flux ropes, apart from the blobs, may comprise different morphological groups with a cluster behavior; the blobs instead span a wide range of longitudes. This finding may hint at either the three-dimensionality of the post-CME current sheet (CS) or the influence of the ambient corona in the evolutionary behavior of the CS. Importantly, we show that the global appearance of the CME can be very different in WISPR (0.11–0.16 AU) and the instruments near 1 AU because of the shorter line-of-sight integration of WISPR.