# Study on Precursor Activity of the X1.6 Flare in the Great AR 12192 with SDO, IRIS, and Hinode

## TL;DR

This study investigates the precursor activity of the X1.6 solar flare in AR 12192, revealing how localized chromospheric flows and magnetic changes contribute to flare onset through multi-instrument analysis.

## Contribution

It provides new insights into the role of chromospheric precursor brightening and localized flows in triggering large-scale solar flares, linking lower atmospheric activity to coronal destabilization.

## Key findings

- Detected significant blueshift (~100 km/s) related to precursor brightening.
- Observed destabilization of large-scale coronal loops post-precursor.
- Indicated magnetic reconnection in the chromosphere triggers coronal flare.

## Abstract

The physical properties and its contribution to the onset of solar flare are still unclear although chromospheric brightening is considered a precursor phenomenon of flare. Many studies suggested that photospheric magnetic field changes cause destabilization of large-scale coronal structure. We aim to understand how a small photospheric change contributes to a flare and to reveal how the intermediary chromosphere behaves in the precursor phase. We analyzed the precursor brightening of the X1.6 flare on 2014 October 22 in the AR 12192 using the Interface Region Imaging Spectrograph (IRIS) and Hinode/EUV Imaging Spectrometer (EIS) data. We investigated a localized jet with the strong precursor brightening, and compared the intensity, Doppler velocity, and line width in C II, Mg II k, Si IV lines by IRIS and He II, Fe XII, Fe XV lines by Hinode/EIS. We also analyzed photospheric magnetic field and chromospheric/coronal structures using Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA). We found a significant blueshift (~ 100 km/s), which is related to the strong precursor brightening over a characteristic magnetic field structure, and the blueshift was observed at all the temperature. This might indicate that the flow is accelerated by Lorentz force. Moreover, the large-scale coronal loop that connects the foot-points of the flare ribbons was destabilized just after the precursor brightening with the blueshift. It suggests that magnetic reconnection locally occurred in the lower chromosphere and it triggered magnetic reconnection of the X1.6 flare in the corona.