# Two-step evolution of a rising flux rope resulting in a confined solar flare

## TL;DR

This study combines observations to analyze a confined solar flare triggered by a rising flux rope, revealing a two-step evolution involving magnetic reconnection and twist transfer, with implications for flare confinement.

## Contribution

It provides detailed observational evidence of flux rope evolution and external reconnection processes leading to confined flares, highlighting the role of twist transfer to large-scale loops.

## Key findings

- Flux rope formed by shearing motions and rose due to kink instability.
- Flux rope's twist reached -1.76 before eruption.
- External reconnection transferred twist to large-scale loops.

## Abstract

Combining the Solar Dynamics Observatory and the New Vacuum Solar Telescope observations, we study a confined flare triggered by a rising flux rope within the trailing sunspots of active region 12733. The flux rope lying above the sheared polarity inversion line can be constructed through magnetic extrapolation but could not be detected in multi-wavelength images at the pre-flare stage. The conspicuous shearing motions between the opposite-polarity fields in the photosphere are considered to be responsible for the flux rope formation. The maximum twist of the flux rope is as high as -1.76, and then the flux rope rises due to the kink instability. Only when the flare starts can the flux rope be observed in high-temperature wavelengths. The differential emission measure results confirm that this flux rope is a high-temperature structure. Associated with the rising flux rope, there appear many post-flare loops and a pair of flare ribbons. When the rising flux rope meets and reconnects with the large-scale overlying field lines, a set of large-scale twisted loops are formed, and two flare ribbons propagating in opposite directions appear on the outskirts of the former ribbons, indicating that the twist of the flux rope is transferred to a much larger system. These results imply that the external reconnection between the rising flux rope and the large-scale overlying loops plays an important role in the confined flare formation.