Understanding the Evolution of the Three-part Structure of a Coronal Mass Ejection Using Multiviewpoint Observations

Abstract The three-part structure (bright front, dark cavity, and bright core) of coronal mass ejections (CMEs) in white-light (WL) coronagraphic images has been studied for decades. However, traditional interpretations in terms of CME substructures have been challenged recently, leaving open questions on their unambiguous identifications. We study a CME that erupted on 2012 July 26, showing a classic three-part structure in MLSO/MK4 and SOHO/LASCO images associated with an eruptive prominence. The CME can be continuously tracked from the low to high corona by combining extreme-ultraviolet (EUV) and WL multiviewpoint observations. Before the eruption, the EUV observations showed that the prominence was suspended at the base of a dark cavity, which is interpreted as evidence of a magnetic flux rope (MFR) structure. We trace the kinematic and morphological evolution of the CME substructures across EUV and WL passbands to link observational signatures to their physical structures. We find that the dark cavity exhibited consistent morphological and kinematic evolution from the low corona in the EUV to the middle and high corona in WL, indicating its continuous association with the MFR structure. Similarly, we find that the bright core region in WL corresponded to the eruptive prominence, both morphologically and kinematically. Given that the bright core observed when the CME was in the high corona was significantly extended and propagated coherently with the CME, we deduce that it was situated inside the CME MFR, as it required additional magnetic support.