EDP Sciences
Free access
Volume 393, Number 2, October II 2002
Page(s) 693 - 701
Section Physical and chemical processes
DOI http://dx.doi.org/10.1051/0004-6361:20011026

A&A 393, 693-701 (2002)
DOI: 10.1051/0004-6361:20011026

Diffusion velocity and reactive thermal conductivity for shock waves propagating in the hydrogen gas

H. Le Coroller and D. Gillet

Observatoire de Haute-Provence - CNRS, 04870 Saint-Michel l'Observatoire, France

(Received 5 June 2002 / Accepted 12 July 2002)

Large gradients of the temperature and ionization degree in shock waves lead to diffusion of ions with respect to neutral atoms. In order to take into account this phenomenon, we modify the fluid dynamics equations of the shock wave model described by Fadeyev & Gillet (2000). The principal goal of our study was to determine the reactive thermal conductivity. We obtained the non-LTE equation for the reactive thermal conductivity for the nonequilibrium two-temperature gas consisting of heavy particles (ions and neutral atoms) and free electrons. For the single temperature gas in LTE our expressions become the same as those

given by Devoto (1967) and Nowak & Ulmschneider (1977). Finally, we discuss the importance of the heat flux induced by the reactive conductivity for shock waves propagating through hydrogen gas with typical properties for atmospheres of pulsating stars ( $10^{-7}~{\rm gm}~{\rm cm}^{-3}\leq \rho \leq 10^{-10}~{\rm gm}~{\rm cm}^{-3}$ and $3000 \:\mathrm{K}\leq T \leq 8000 \:\mathrm{K}$). The reactive conductivity could be efficient behind the shock front, at the end of the thermalization zone when ionization process brutally occurs. When the gas is very dense, the reactive heat flux is of the same order of magnitude as the classical electronic heat flux.

Key words: conduction -- shock waves -- hydrodynamics -- stars: atmospheres

Offprint request: H. Le Coroller, coroller@obs-hp.fr

© ESO 2002