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Nonthermal distributions in the solar and stellar coronae
J. Dudík 1,2, E. Dzifčáková 2, M. Karlický 2, A. Kulinová 1,2 1 – DAPEM, Faculty of Mathematics, Physics and Informatics, Comenius University, Slovakia 2 – Astronomical Institute, Academy of Sciences of the Czech Republic Radiative (M)-HD Seminary, April 14th, 2011, Ondřejov
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Outline I. The nonthermal distributions k–distributions
n–distributions Why nonthermal distributions? Definition and basic properties, the pseudotemperature II. Radiative-loss function in solar and stelar coronae Contributions from lines and continuum Bremsstrahlung Contribution from individual elements or ions Consequences III. The nonthermal continuum Bremsstrahlung continuum in X-rays and radio Free-bound continuum and flare diagnostics
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k-distributions: definition
Owocki & Scudder (1983), Dzifčáková (2006a): k Maxwellian distribution
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Fe Ionization equilibrium
Dzifčáková (2002): Changes in the Fe IX – XVI ionization equilibrium for the k-distributions with respect to Maxwellian one are significant:
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k-distributions: why Study the emission – need to know about the microphysics Suprathermal component (“high-energy tail”) present during flares and also in solar wind Maksimovic et al. (1997): solar wind velocity distribution is better approximated by one k-distribution than with one or sum of two Maxwellians Collier (2004): if the mean particle energy is not held constant, the entropy is not maximalized by a Maxwellian, but by the k-distribution Tsallis (1988), Leubner et al. (2002, 2005, 2008) – non-extensive theory Dudík et al. (2009): considerable influence on the EUV filter responses Dzifčáková & Kulinová (2010, 2011) - k-distribution diagnosed in transition region spectra (Si III line ratios) and in flares (Fe XII line ratios) Their presence in AR corona is still an open question. Nevertheless...
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Dzifčáková & Kulinová (2010)
Solar Phys., 263, 25
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n-distributions: definition
Seely, Feldman & Doschek (1987), Dzifčáková & Tóthová (2007): n = 1 Maxwellian distribution Pseudo-temperature t :
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n-distributions: why/when
Consistent with X-Ray spectra observed with flares (Dzifčáková et al. 2008, A&A 488, 311; Kulinová et al., 2011, A&A, subm.)
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The radiative losses II.
Emissivity eij of a spectral line line – transition from the level i to level j in a k-times ionized element x is given by: FIP effect Radiative losses ER:
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Synthetic line spectra
Modification of CHIANTI, spectra for C,N,O,Ne,Mg,Al,Si,S,Ar,Ca,Fe,Ni
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Nonthermal bremsstrahlung
For Maxwellian distribution: For the k-distributions (Dudík et al., 2011, A&A, in press):
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Atomic data errors
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Bremsstrahlung spectrum
III. Bremsstrahlung spectrum
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Bremsstrahlung - spectrum
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Freebound continuum
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Freebound continuum
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Conclusions Conditions in solar corona allow for non-thermal distributions. Their influence on the radiative losses is much higher than other effects Total radiative losses are lower for k-distributions, lesser requirement for heating input higher for n-distributions cooling processes for flares Crucial for theoretical modeling of the solar corona and flares Spectral synthesis for nonthermal distributions now complete new diagnostic possibility for flare spectra
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