# Pre-flare processes, flux rope activation, large-scale eruption and associated X-class flare from the active region NOAA 11875

## TL;DR

This study analyzes the pre-flare processes, flux rope activation, and eruption leading to an X-class flare in NOAA 11875, revealing how pre-flare activity can destabilize magnetic flux ropes and trigger large-scale eruptions.

## Contribution

It provides detailed multi-wavelength observations showing the evolution of a flux rope from pre-flare to eruption, highlighting the feedback between CME dynamics and magnetic reconnection.

## Key findings

- Pre-flare activity within a stable flux rope can trigger eruption.
- Transition from slow rise to fast acceleration bifurcates flare phases.
- Eruption associated with type III radio bursts and high-energy X-ray sources.

## Abstract

We present a multi-wavelength analysis of the eruption of a hot coronal channel associated with an X1.0 flare (SOL2013-10-28T02:03) from the active region NOAA 11875 by combining observations from AIA/SDO, HMI/SDO, RHESSI, and HiRAS. EUV images at high coronal temperatures indicated the presence of a hot channel at the core of the active region from the early pre-flare phase evidencing the pre-existence of a quasi-stable magnetic flux rope. The hot channel underwent an activation phase after a localized and prolonged pre-flare event occurring adjacent to one of its footpoints. Subsequently, the flux rope continued to rise slowly for $\approx$16 min during which soft X-ray flux gradually built-up characterizing a distinct precursor phase. The flux rope transitioned from the state of slow rise to the eruptive motion with the onset of the impulsive phase of the X1.0 flare. The eruptive expansion of the hot channel is accompanied by a series of type III radio bursts in association with impulsive rise of strong hard X-ray non-thermal emissions that included explicit hard X-ray sources of energies up to $\approx$50 keV from the coronal loops and $\approx$100 keV from their footpoint locations. Our study contains evidence that pre-flare activity occurring within the spatial extent of a stable flux rope can destabilize it toward eruption. Moreover, sudden transition of the flux rope from the state of slow rise to fast acceleration precisely bifurcated the precursor and the impulsive phases of the flare which points toward a feedback relationship between early CME dynamics and the strength of the large-scale magnetic reconnection.