# High-resolution observations of flare precursors in the low solar atmosphere

## TL;DR

This study uses high-resolution solar observations to analyze flare precursors in the low atmosphere, revealing small-scale magnetic interactions that may trigger larger solar flares.

## Contribution

It provides the first high-resolution observations linking low-atmospheric magnetic channels to flare precursors and the onset of solar flares.

## Key findings

- Precursor brightenings originate from small-scale magnetic channels.
- Magnetic flux and current enhancements are observed at precursor sites.
- Emerging magnetic fields interact with sheared arcades to trigger flares.

## Abstract

Solar flares are generally believed to be powered by free magnetic energy stored in the corona, but the build up of coronal energy alone may be insufficient for the imminent flare occurrence. The flare onset mechanism is a critical but less understood problem, insights into which could be gained from small-scale energy releases known as precursors, which are observed as small pre-flare brightenings in various wavelengths, and also from certain small-scale magnetic configurations such as the opposite polarity fluxes, where magnetic orientation of small bipoles is opposite to that of the ambient main polarities. However, high-resolution observations of flare precursors together with the associated photospheric magnetic field dynamics are lacking. Here we study precursors of a flare using unprecedented spatiotemporal resolution of the 1.6 m New Solar Telescope, complemented by novel microwave data. Two episodes of precursor brightenings are initiated at a small-scale magnetic channel (a form of opposite polarity fluxes) with multiple polarity inversions and enhanced magnetic fluxes and currents, lying near the footpoints of sheared magnetic loops. The low-atmospheric origin of these precursor emissions is corroborated by microwave spectra. We propose that the emerging magnetic channel field interacts with the sheared arcades to cause precursor brightenings at the main flare core region. These high-resolution results provide evidence of low-atmospheric small-scale energy release and possible relationship to the onset of the main flare.