Linear Thermal Instability and Fluctuations in Molecular Clouds

Evidence of small-scale condensations in the magnetic molecular clouds has been accumulating over the past decades through radio and optical/ultraviolet observations. The origin and shape of these small-scale condensations is a disputable issue. Nejad-Asghar & Ghanbari (2004 hereafter NG) have recently studied the effect of the linear thermal instability on the formation of fluctuations in molecular clouds. The authors inferred that under certain conditions (e.g., depending on expansion or contraction of the background) thermal instability and ambipolar diffusion can produce spherical, oblate, or prolate condensations.