Andretta, V. ; Bemporad, A. ; De Leo, Y. ; Jerse, G. ; Landini, F. ; Mierla, M. ; Naletto, G. ; Romoli, M. ; Sasso, C. ; Slemer, A. ; Spadaro, D. ; Susino, R. ; Talpeanu, D.-C. ; Telloni, D. ; Teriaca, L. ; Uslenghi, M. ; Antonucci, E. ; Auchère, F. ; Berghmans, D.

published in Astronomy and Astrophysics, Volume 656, id.L14, 10 pp.

Abstract: Context. The Metis coronagraph on-board Solar Orbiter offers a new view of Coronal Mass Ejections (CMEs), observing them for the first time with simultaneous images acquired with a broad-band filter in the visible light interval, and with a narrow-band filter around the H i Ly-α line at 121.567 nm, the so-called Metis UV channel. Aims. We show the first Metis observations of a CME, obtained on 16 and 17 January 2021. The event was observed also by the EUI/FSI imager on board Solar Orbiter, as well as by other space-based coronagraphs, such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here with Metis data. Methods. Different images are analyzed here to reconstruct with the Graduated Cylindrical Shell model the 3D orientation of the expanding CME flux-rope. This allows also to identify the possible location of the source region. Measurements of the CME kinematics allow to quantify the expected Doppler dimming in the Ly-α channel. Results. Observations show that most CME features seen in the visible-light images are also seen in the Ly-α images, although some features in the latter channel appear more structured than their visible-light counterparts. We estimated the expansion velocity of this event to be below 140 km s−1. Hence, these observations can be understood by assuming that Doppler dimming effects do not strongly reduce the Ly-α emission from the CME. These velocities are comparable or smaller than the radial velocities inferred with the same data in a similar coronal structure on the East side of the Sun. Conclusions. The first observations by Metis of a CME demonstrate the capability of the instrument to provide valuable and novel information on the structure and dynamics of those coronal events. Considering also its diagnostics capabilities of the conditions of the ambient corona, Metis promises to significantly advance our knowledge of such phenomena.

Keyword(s): Sun:atmosphere ; Sun:corona ; Sun:UV radiation ; Sun:coronal mass ejections( CMEs) ; Solar Orbiter ; EUI
DOI: 10.1051/0004-6361/202142407