Evaluation of different recipes for chromospheric radiative losses in solar flares

TL;DR

This study evaluates various approximate recipes for chromospheric radiative losses in solar flare simulations, comparing their accuracy against detailed calculations to determine their suitability and limitations.

Contribution

The paper systematically assesses the performance of different radiative loss recipes in flare simulations, highlighting their discrepancies and applicability across different atmospheric layers.

Findings

GF90 and HCD22 recipes approximate total radiative losses well.

Discrepancies exist in atmospheric layer predictions during flare evolution.

GF90 overestimates cooling in the upper chromosphere at high temperatures.

Abstract

Context. Radiative losses are an indispensable part in the numerical simulation of flares. Detailed calculations could be computationally expensive, especially in the chromosphere. There have been some approximate recipes for chromospheric radiative losses in flares, yet their feasibility in flare simulations needs further evaluation. Aims. We aim to evaluate the performance of different recipes for chromospheric radiative losses in flare simulations. Methods. We compare the atmospheric structure and line profiles in beam-heated flares calculated with detailed radiative losses and the approximate recipes. Results. Both GF90 and HCD22 recipes provide acceptable total radiative losses compared with detailed one, but there are discrepancies in the different atmospheric layers during the different evolutionary phases, which leads to misestimations of temperature and line intensity. The recipe of GF90 overestimates the coolings in the upper chromosphere greatly when temperature exceeds 10^5 K, which also affects the flare evolution and line asymmetries. Radiative heating in the middle chromosphere only functions in the initial stage and could be safely neglected. However, radiative heating from Lyman continuum could dominate near the transition region.