An Observational Study On A Solar Magnetic Breakout Eruption

The fundamental mechanism initiating coronal mass ejections?CMEs?remains controversial.One of the leading theories is magnetic breakout,in which magnetic reconnection occurring high in the corona removes the confinement on an energized low-corona structure from the overlying magnetic field,thus allowing it to erupt.This mechanism is first put forward by Antiochos.Earlier studies have presented numerical simulation results and observational analysis to understand this mechanism.Yet,few studies report direct observation of magnetic breakout,especially the triggering breakout reconnection.Here,we report observational evidence of this elusive breakout reconnection in a multi-polar magnetic configuration that leads to a CME and an X-class,long-duration flare,occurred at the southwest limb on 2014 April 25.Combining coronal EUV X-ray,and microwave data.We have analyzed the evolution,morphology,kinematics and reconnection of the event.The occurrence of breakout reconnection is supported by the presence of pairs of heated cusp-shaped loops around an X-type structure and signatures of reconnection inflows.Other peculiar features new to the breakout picture include sequential loop brightening,coronal hard X-rays at energies up to?100 keV,and extended high-corona X-rays above the later restored multi-polar structure.These observations,from a novel perspective with clarity never achieved before,present crucial clues to understanding the initiation mechanism of solar eruptions.In addition,we also briefly analyze the HXR dual-source struction corresponding to this case,and propose a new physical explanation for this dual-source structure.In the flare recovery phase,at 131 A and 94 A,of high temperature we can see a spatially-extended source in the high corona,while at relatively low temperatures of 193 A and 304 A we do not observe this phenomenon.Through the NoRH microwave imaging analysis,we found that the EUV source have counterparts in both SXRs and microwaves.The extended source is spatially separated from the low lying flare radiation source.This is very different from that observed in usual events.In addition,the bright temperature of the microwave radiation source appearing in the flare recovery increase with time,up to 2.5*10⁴ K.With the EUV?DEM analysis?microwave and X-ray data,the diagnosed the source and found that the temperature of the source is 1*10⁷ K and the density is 10²⁸cm^-5.The spectral fit of the RHESSI data shows that the thermal components of the source region dominate,mainly for bremsstrahlung of thermal electrons.