Evaluation of different recipes for chromospheric radiative losses in solar flares

Context. Radiative losses are an indispensable part in the numerical simulation of flares. Detailed calculations could be computa- tionally 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 di ff erent 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 discrep- ancies in the di ff erent atmospheric layers during the di ff erent 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 a ff ects 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.