Genesis of a Confined X6.4 Flare in a Quadrupolar Magnetic Configuration

Abstract

Both eruptive and confined flares—those having and lacking, respectively, an associated large-scale coronal mass ejection—are frequently observed in solar active regions (ARs). The physical mechanisms controlling the nature of these flares are poorly understood, requiring a detailed investigation of both the magnetic environment and the dynamic flare production process within the source region. Here we study a confined X6.4 flare with a failed filament eruption in AR 13590, observed by the SDO spacecraft on 2024 February 22. AR 13590 exhibited a quadrupolar magnetic configuration consisting of one central and two side arcades of low-lying loops, overlain by a fourth arcade of high-lying loops. A potential-field extrapolation contains a low-altitude null point at a height of approximately 5 Mm. This is a classic magnetic-breakout topology, except that the rising filament lay under one of the side arcades. The confined flare generated four ribbons located in all four of the major polarities, and proceeded in two phases, characterized by two successive stages of ribbon brightenings accompanied by forward and then reverse motion of the brightenings along the interior ribbons. We propose that the two phases represent breakout reconnection in the null region, which removed the flux ahead of the rising filament, followed by “anti-breakout” reconnection, corresponding to a reversed process as those flux systems evolved back toward the pre-eruption configuration. We discuss the implications of these observations for understanding how intense flares can occur without the expulsion of material from the solar corona.