# Different Signatures of Chromospheric Evaporation in Two Solar Flares Observed with IRIS

## TL;DR

This study compares signatures of chromospheric evaporation in two solar flares observed with IRIS, revealing both gentle and explosive evaporation signatures through spectral line shifts, providing new insights into flare dynamics.

## Contribution

It identifies and contrasts gentle and explosive chromospheric evaporation signatures in two solar flares using IRIS spectral data, highlighting new observational features.

## Key findings

- Gentle evaporation shows blueshifts with velocities up to 20 km/s.
- Explosive evaporation exhibits redshifts with velocities from several to tens of km/s.
- First report of gentle evaporation manifested as blueshifts in cool lines in IRIS observations.

## Abstract

We present different signatures of chromospheric evaporation in two solar flares observed by the Interface Region Imaging Spectrograph (IRIS). In the B1.6 flare on 2016 December 6 (SOL2016-12-06T10:40), the transition region Si IV line and the chromospheric C II and Mg II lines show blueshifts with low velocities up to 20 km/s at the flare loop footpoints in the rise phase, indicative of a gentle chromospheric evaporation. While in the C1.6 flare on 2015 December 19 (SOL2015-12-19T10:51), the Si IV, C II, and Mg II lines exhibit redshifts with velocities from several to tens of km/s at the footpoints, which might suggest an explosive chromospheric evaporation. Explosive evaporation has been observed in many flares that were captured by IRIS; however, gentle evaporation, especially manifested as blueshifts in the cool Si IV, C II, and Mg II lines, has scarcely been reported. Our results bring some new insights into chromospheric evaporation in the IRIS era.