C.D.S. - SIMBAD4 rel 1.7 - 2020.07.10CEST02:55:52

2011A&A...529A.103D - Astronomy and Astrophysics, volume 529A, 103-103 (2011/5-1)

The bound-bound and free-free radiative losses for the nonthermal distributions in solar and stellar coronae.


Abstract (from CDS):

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 for nonthermal κ- and n-distributions. The bound-bound radiative losses are computed by integrating synthetic spectra. An analytical expression is derived for nonthermal bremsstrahlung. 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 greater than the errors due to the missing contribution of the free-bound continuum or errors in atomic data. For κ-distributions, the radiative-loss functions are in general weaker than for Maxwellian distribution, with a 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 only changes by a few percent except in the extreme nonthermal case of κ = 2. Stability analysis reveals that the X-ray loops are stable against the radiatively-driven thermal instability.

Abstract Copyright:

Journal keyword(s): atomic processes - radiation mechanisms: non-thermal - Sun: corona - Sun: X-rays, gamma rays - instabilities

VizieR on-line data: <Available at CDS (J/A+A/529/A103): rloss_k.dat rloss_n.dat>

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