Abstract
A model of a nonhomogeneous dust cloud is explored in order to find the effective scale length at which the dust temperature fluctuates around the critical temperature for H2 formation on dust grains. The distribution of the grain temperature in the cloud is studied using equations of heat balance and radiative transfer in the Eddingtonlike approximation derived by Giovanelli (1959, 1963) for nonhomogeneous media. The radiative heating problem is solved analytically, in a first approximation, for a semiinfinite cloud model with transverse fluctuations in extinction for several parameters, including the albedo for single scattering, the greenhouse parameter, the amplitude of the fluctuations, and a parameter which measures the optical thickness of the density fluctuations. The aim of the paper is to determine whether density inhomogeneities can produce spatial temperature variations which would produce fluctuations in the rate formation of the hydrogen molecule such as those suggested by Reddish (1975).
