Nonlinear thermal instability in a nonstationary medium. Evolution of density fluctuations

Formation of the inhomogeneous structure of hot gases of galaxy clusters as a result of development of thermal instability is considered. Evolution of different unstable perturbation modes is discussed. One-dimensional gas dynamic models of evolution of density fluctuations are calculated. Effect of the perturbation spectrum and the initial temperature of a gas on the properties of inhomogeneities forming up to the moment when condensation gas cools up to T∼104K. Effect of thermal conductivity is simulated by introduction of a threshold wave length in the spectrum of initial perturbations. It is shown that compact condensations containing <or approx.30% og fas total mass as a result of gas cooling with T<or approx. 107K are formed. Density contrast reaching values <or approx.103 depends on the perturbation spectrum, efficiency and thermal conductivity and on the magnetic field nature