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Description
The radiative-loss function is an important ingredient in the physics of the solar corona, transition region and flares. We investigate the radiative losses due to the bound-bound transitions and bremsstrahlung and bremsstrahlung for nonthermal {kappa}- and n-distributions. The bound-bound radiative losses are computed by integration of synthetic spectra. Analytical expression for nonthermal bremsstrahlung is derived. The bremsstrahlung is computed numerically using accurate values of the free-free Gaunt factor. We find that the changes in radiative-loss functions due to nonthermal distributions are several times larger than the errors due to missing contribution of the free-bound continuum or errors in atomic data. For {kappa}-distributions, the radiative-loss functions are in general lesser than for Maxwellian distribution, with few exceptions caused by the behavior of Fe. The peaks of the radiative-loss functions are in general flatter. The situation is opposite for n-distributions, for which the radiative-loss functions have higher and narrower peaks. Local minima and maxima of the radiative-loss functions may also be shifted. The contribution from bremsstrahlung change only by few percent except the extreme nonthermal case of {kappa}=2. Stability analysis reveals that the X-ray loops are stable against the radiatively-driven thermal instability.
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