Volume 656, December 2021
Solar Orbiter First Results (Cruise Phase)
|Number of page(s)||10|
|Section||Letters to the Editor|
|Published online||14 December 2021|
Letter to the Editor
The first coronal mass ejection observed in both visible-light and UV H I Ly-α channels of the Metis coronagraph on board Solar Orbiter⋆
INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Naples, Italy
2 INAF – Osservatorio Astrofisico di Torino, Turin, Italy
3 Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
4 INAF – Osservatorio Astronomico di Trieste, Trieste, Italy
5 Royal Observatory of Belgium, Brussels, Belgium
6 Institute of Geodynamics of the Romanian Academy, Bucharest, Romania
7 Università di Padova – Dip. Fisica e Astronomia “Galileo Galilei”, Padua, Italy
8 CNR – Istituto di Fotonica e Nanotecnologie, Padua, Italy
9 INAF – Associate Scientist, Italy
10 Università di Firenze – Dip. Fisica e Astronomia, Florence, Italy
11 INAF – Osservatorio Astrofisico di Catania, Catania, Italy
12 KU Leuven, Leuven, Belgium
13 INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan, Italy
14 Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France
15 University of Wrocław – Astronomical Institute, Poland
16 Università di Catania – Dip. Fisica e Astronomia “Ettore Majorana”, Catania, Italy
17 Università di Padova – CISAS, Padua, Italy
18 Catholic University of America, Washington, DC, USA
19 Università di Urbino “Carlo Bo” – DiSPeA, Urbino, Italy
20 INFN – Sez. Firenze, Florence, Italy
21 Astronomical Institute of the Czech Academy of Sciences, Ondřejov, Czech Republic
22 Università di Torino, Turin, Italy
23 Politecnico di Torino – DET, Turin, Italy
24 NASA HQ, Washington, DC, USA
25 CNR – IEIIT, Padua, Italy
26 Agenzia Spaziale Italiana, Roma, Italy
27 INAF – Istituto di Astrofisica e Planetologia Spaziali di Roma, Rome, Italy
28 INAF – Osservatorio Astronomico di Palermo, Palermo, Italy
29 Laboratoire Atmosphères, Milieux et Observations Spatiales, Guyancourt, France
30 Università di Pavia, Pavia, Italy
31 Università di Padova, Padua, Italy
32 Università della Calabria – Dip, Fisica, Italy
33 Università di Palermo – Dip. Fisica e Chimica “Emilio Segrè”, Palermo, Italy
34 Naval Research Laboratory, Washington, DC, USA
35 University of Athens, Dep. Physics, Athens, Greece
36 University of California, Los Angeles, California, USA
Accepted: 28 October 2021
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 also observed 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 analysed here to reconstruct the 3D orientation of the expanding CME flux rope using the graduated cylindrical shell model. This also allows us to identify the possible location of the source region. Measurements of the CME kinematics allow us 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 with or smaller than the radial velocities inferred from 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 these coronal events. Considering also its diagnostics capabilities regarding the conditions of the ambient corona, Metis promises to significantly advance our knowledge of such phenomena.
Key words: Sun: atmosphere / Sun: corona / Sun: UV radiation / Sun: coronal mass ejections (CMEs)
Movies are available at https://www.aanda.org
© ESO 2021
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