A multiple spacecraft detection of the 2 April 2022 M-class flare and filament eruption during the first close Solar Orbiter perihelion
Authors: Janvier M. , Mzerguat S. , Young P. R. , Buchlin É. , Manou A. , Pelouze G. , Long D. M. , Green L. , Warmuth A. , Schuller F. , Démoulin P. , Calchetti D. , Kahil F. , Bellot Rubio L. , Parenti S. , Baccar S. , Barczynski K. , Harra L. K. , Hayes L. A. , Thompson W. T. , Müller D. , Baker D. , Yardley S. , Berghmans D. , Verbeeck C. , Smith P. J. , Peter H. , Aznar Cuadrado R. , Musset S. , Brooks D. H. , Rodríguez L. , Auchère F. , Carlsson M. , Fludra A. , Hassler D. , Williams D. , Caldwell M. , Fredvik T. , Giunta A. , Grundy T. , Guest S. , Kraaikamp E. , Leeks S. , Plowman J. , Schmutz W. , Schühle U. , Sidher S. D. , Teriaca L. , Solanki S. K. , del Toro Iniesta J. C. , Woch J. , Gandorfer A. , Hirzberger J. , Orozco Suárez D. , Appourchaux T. , Valori G. , Sinjan J. , Albert K. , Volkmer R. 
Published: July 2023

Context. The Solar Orbiter mission completed its first remote-sensing observation windows in the spring of 2022. On 2 April 2022, an M-class flare followed by a filament eruption was seen both by the instruments on board the mission and from several observatories in Earth’s orbit, providing an unprecedented view of a flaring region with a large range of observations.
Aims. We aim to understand the nature of the flaring and filament eruption events via the analysis of the available dataset. The complexity of the observed features is compared with the predictions given by the standard flare model in 3D.
Methods. In this paper, we use the observations from a multi-view dataset, which includes extreme ultraviolet (EUV) imaging to spectroscopy and magnetic field measurements. These data come from the Interface Region Imaging Spectrograph, the Solar Dynamics Observatory, Hinode, as well as several instruments on Solar Orbiter.
Results. The large temporal coverage of the region allows us to analyse the whole sequence of the filament eruption starting with its pre-eruptive state. Information given by spectropolarimetry from SDO/HMI and Solar Orbiter PHI/HRT shows that a parasitic polarity emerging underneath the filament is responsible for bringing the flux rope to an unstable state. As the flux rope erupts, Hinode EIS captures blue-shifted emission in the transition region and coronal lines in the northern leg of the flux rope prior to the flare peak. This may be revealing the unwinding of one of the flux rope legs. At the same time, Solar Orbiter SPICE captures the whole region, complementing the Doppler diagnostics of the filament eruption. Analyses of the formation and evolution of a complex set of flare ribbons and loops, of the hard and soft X-ray emissions with STIX, show that the parasitic emerging bipole plays an important role in the evolution of the flaring region.
Conclusions. The extensive dataset covering this M-class flare event demonstrates how important multiple viewpoints and varied observations are in order to understand the complexity of flaring regions. While the analysed data are overall consistent with the standard flare model, the present particular magnetic configuration shows that surrounding magnetic activity such as nearby emergence needs to be taken into account to fully understand the processes at work. This filament eruption is the first to be covered from different angles by spectroscopic instruments, and provides an unprecedented diagnostic of the multi-thermal structures present before and during the flare. This complete dataset of an eruptive event showcases the capabilities of coordinated observations with the Solar Orbiter mission.