# Energy Build-up and Triggering Leading to a M1.5 Flare on 1 August 2014

## TL;DR

This study investigates the energy build-up and triggering mechanisms of an M1.5 solar flare on August 1, 2014, highlighting the roles of sunspot rotation, magnetic flux emergence, and helicity injection.

## Contribution

It provides new insights into how large-scale flux emergence and small-scale magnetic activities collectively trigger solar flares.

## Key findings

- Sunspot rotations occurred before the flare, involving both clockwise and counter-clockwise motions.
- Magnetic helicity injection was observed to reverse sign after the flare.
- Small-scale magnetic flux emergence was identified as a key trigger for the flare.

## Abstract

The energy storage and trigger mechanisms of solar flares are important for understanding of solar activity. We analyzed multi-wavelength observations of a M1.5 flare on 1 August 2014, in active region NOAA 12127 (SOL2014-08-01T18:13). There are evident large scale sunspot rotations in positive magnetic field of the main energy release region before the eruption; the rotations contain both clockwise and counter-clockwise directions. Injection of magnetic helicity from the photosphere prior to the flare. The sign of the helicity injection is reversed after the flare. It is found that both persistent larger scale ($\approx$ one day) and impulse smaller scale ($\approx$ one to two hours) magnetic-flux emergences are associated with the flare. We conclude that larger-scale flux emergence, helicity injection and sunspot rotation contribute to the energy build up, while the small-scale magnetic-flux emergence plays crucial role in triggering the flare.