J/A+A/529/A103 Radiative losses in solar and stellar coronae (Dudik+, 2011)
The bound-bound and free-free radiative losses for the nonthermal distributions
in solar and stellar coronae.
Dudik J., Dzifcakova E., Karlicky M., Kulinova A.
<Astron. Astrophys. 529, A103 (2011)>
=2011A&A...529A.103D 2011A&A...529A.103D
ADC_Keywords: Atomic physics
Keywords: atomic processes - radiation mechanisms: non-thermal -
Sun: corona - stars: coronae - Sun: X-rays, gamma rays - instabilities
Abstract:
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 κ- 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
κ-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 κ=2. Stability
analysis reveals that the X-ray loops are stable against the
radiatively-driven thermal instability.
Description:
The radiative losses due to bound-bound and free-free transitions
calculated for plasma with nonthermal κ- and n-distributions of
electron energies are presented. The radiative losses are calculated
for the values of κ=2, 3, 5, and 10 (rloss_k.dat) and n=1
(Maxwellian), 3, 5, and 11 (rloss_n.dat) as function of temperature
(T) or pseudo-temperature (tau) for the assumed value of electron
density ne=1016m-3. The ne*nH factor is not included in the
calculations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
rloss_k.dat 48 151 Radiative losses for κ-distributions
rloss_n.dat 48 151 Radiative losses for n-distributions
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Byte-by-byte Description of file: rloss_k.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 [K] log(T) [5/8] Temperature (decimal log)
7- 15 E9.3 W/m3 k2 Radiative losses for κ=2
18- 26 E9.3 W/m3 k3 Radiative losses for κ=3
29- 37 E9.3 W/m3 k5 Radiative losses for κ=5
40- 48 E9.3 W/m3 k10 Radiative losses for κ=10
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Byte-by-byte Description of file: rloss_n.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 [K] log(tau) [5/8] Pseudo-Temperature (decimal log) (1)
7- 15 E9.3 W/m3 n1 Radiative losses for n=1 (1)
18- 26 E9.3 W/m3 n3 Radiative losses for n=3
29- 37 E9.3 W/m3 n5 Radiative losses for n=5
40- 48 E9.3 W/m3 n11 Radiative losses for n=11
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Note (1): τ=(n+2)T/3; n=1 is the Maxwellian distribution.
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Acknowledgements:
J. Dubik, dudik(at)fmph.uniba.sk, DAPEM, FMPhI, Comenius Univ., Slovakia
(End) J. Dudik [DAPEM], Patricia Vannier [CDS] 03-Mar-2011