Beyond Large-scale Descriptions of Coronal Mass Ejections: Quantifying Their Substructures in Three Dimensions

Abstract Coronal mass ejections (CMEs) are usually characterized by their large-scale properties, even though smaller-scale structures are clearly evident, particularly in observations obtained closer to the Sun. Since the launch of the Parker Solar Probe (PSP) mission, its Wide-field Imager for Solar Probe (WISPR) telescope has enjoyed unprecedented proximity to CMEs in the upper corona and inner heliosphere and has imaged CME substructure in high spatial and temporal detail. Leveraging these observations, we introduce the novel Multi-pOint Single-observatory AnalysIs of Kinematics in Three Dimensions (MOSAIK3D) method to quantitatively characterize CME substructure observable by WISPR. MOSAIK3D uses apparent substructure flows to enable a detailed determination of kinematics in three dimensions. We demonstrate MOSAIK3D on a CME observed on 2024 September 26 with PSP located at approximately 40 solar radii from the Sun center. From a set of point-like features whose apparent two-dimensional speed is inferred using optical flows, we exploit PSP’s fast angular speed to recover their coordinates in three dimensions in qualitative agreement with the graduated cylindrical shell model of the full CME. We then render a contiguous, homogeneous three-dimensional volume of the CME substructure via a convex hull methodology. The recovered kinematics and dynamics offer the most detailed analysis of CME substructure to date, showcasing that the bulk CME properties obtained from global modeling are, in fact, gross simplifications of a significantly more complex and intriguing dynamical evolution at finer scales. We offer a preview of the capabilities of the MOSAIK3D analysis and its potential applications in future work.