Solar Eruption Onset and Particle Acceleration in Nested-Null Topologies

Abstract

The magnetic breakout model explains a variety of solar eruptions, ranging from small-scale jets to large-scale coronal mass ejections (CMEs). Most of our previous studies are focused on jets and CMEs in single null-point topologies. Here, we investigate the initiation of CMEs and associated particle acceleration in a double null-point (or nested fan-spine) topology during multiple homologous M- and X-class flares from an active region. The initiation of the flare and associated eruption begins with inflow structures moving towards the inner null of the closed fan-spine topology. The first explosive breakout reconnection of the flux rope at the inner null produced a circular and remote ribbons along with successful eruption of the flux rope and associated fast EUV (shock) wave. Simultaneous flare reconnection beneath the erupting flux rope produced a typical two-ribbon flare along with two hard X-ray footpoint sources. When the flux rope (with shock) reaches the outer null, the second explosive breakout reconnection produces another large-scale remote ribbon. The radio observations reveal quasiperiodic Type III bursts (period=100-s) and a Type II burst during the breakout reconnection near the inner and outer nulls, along with gradual solar energetic particles (SEPs) observed at 1 AU for magnetically connected events. This study highlight the importance of two successive breakout reconnection in the initiation of CMEs in nested-null topologies and associated particle acceleration/release into the interplanetary medium. The particles are accelerated by the shock ahead of the flux rope, which formed during the inner breakout reconnection. These findings have significant implications for particle acceleration and escape processes in multi-scale null-point topologies that produce jets and CMEs.