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We present a case study of an M4-class flare on 28 March 2022, near SolarOrbiter's first science perihelion (0.33 AU). Solar Orbiter was 83.5{\deg} westof the Sun-Earth line, making the event appear near the eastern limb, whileEarth-orbiting spacecraft observed it near the disk center. The timing andlocation of the STIX X-ray sources were related to the plasma evolutionobserved in the EUV by the Extreme Ultraviolet Imager (EUI) on Solar Orbiterand the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory,and to the chromospheric response observed in 1600 {\AA} by AIA. We performeddifferential emission measure (DEM) analysis to further characterize theflaring plasma at different subvolumes. The pre-flare magnetic fieldconfiguration was analyzed using a nonlinear force-free (NLFF) extrapolation.In addition to the two classical hard X-ray (HXR) footpoints at the ends of theflaring loops, later in the event we observe a nonthermal HXR source at one ofthe anchor points of the erupting filament. The evolution of the AIA 1600~{\AA}footpoints indicates that this change in footpoint location represents adiscontinuity in an otherwise continuous westward motion of the footpointsthroughout the flare. The NLFF extrapolation suggests that strongly shearedfield lines close to, or possibly even part of, the erupting filamentreconnected with a weakly sheared arcade during the first HXR peak. Theremainder of these field lines reconnected later in the event, producing theHXR peak at the southern filament footpoint. Our results show that thereconnection between field lines with very different shear in the early phaseof the flare plays a crucial role in understanding the motion of the HXRfootpoint during later parts of the flare. This generalizes simpler models,such as whipping reconnection, which only consider reconnection propagatingalong uniformly sheared arcades.

astronomy and astrophysics

Multi-point study of the energy release and transport in the 28 March  2022, M4-flare using STIX, EUI, and AIA during the first Solar Orbiter  nominal mission perihelion