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

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

k-distributions: definition Owocki & Scudder (1983), Dzifčáková (2006a): k   Maxwellian distribution

Fe Ionization equilibrium Dzifčáková (2002): Changes in the Fe IX – XVI ionization equilibrium for the k-distributions with respect to Maxwellian one are significant:

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...

Dzifčáková & Kulinová (2010) Solar Phys., 263, 25

n-distributions: definition Seely, Feldman & Doschek (1987), Dzifčáková & Tóthová (2007): n = 1 Maxwellian distribution Pseudo-temperature t :

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.)

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:

Synthetic line spectra Modification of CHIANTI, spectra for C,N,O,Ne,Mg,Al,Si,S,Ar,Ca,Fe,Ni

Nonthermal bremsstrahlung For Maxwellian distribution: For the k-distributions (Dudík et al., 2011, A&A, in press):

Atomic data errors

Bremsstrahlung spectrum III. Bremsstrahlung spectrum

Bremsstrahlung - spectrum

Freebound continuum

Freebound continuum

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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