Dynamics of the Coronal Magnetic Field in the 2022 October 2 X-class Flare

Abstract Solar flares are driven by the release of free magnetic energy and are often associated with the restructurization of the magnetic field topology. Yet, observations of the evolving magnetic field in the flaring volume are limited to very few cases, including the 2017 September 10 X8.2 limb flare; thus, a verification of whether a similar evolution takes place in other solar flares is needed. Here, we report one more: the 2022 October 2 X1.1-class solar flare, seen on the disk, whose microwave data permit mapping the magnetic field over the flaring source and tracking the magnetic field evolution over the course of the flare. We find that the coronal magnetic field shows a prominent decay with a rate up to 10 G s −1 in several (above the) looptop locations. The magnetic field is also confidently measured at the loop legs and the bottom part of the erupting filament. Prominent acceleration of electrons is detected where the magnetic field decays. We develop 3D models of the flare, whose magnetic field shows resemblance to and also deviation from the magnetic field inferred from the microwave data. This study confirms that the coronal magnetic field decays during the rise phase of the solar flare. The amount of released magnetic energy is sufficient to support other components of the flare energy.