Chemical signatures of the intermittency of turbulence in low density interstellar clouds
E. Falgarone, G. Pineau Des Forets, E. Roueff;
AaA, 1995, 300, 870
ABSTRACT:The space-time intermittent distribution of the dissipation rate of kinetic energy in turbulent interstellar
clouds generates transient and localized hot regions embedded in cooler
gas.
The gas kinetic temperatures reached in low-density clouds, such as H I
clouds, are locally large enough to overcome many activation barriers of gas
phase chemical reactions and significantly increase the endothermic
reaction rates.
Small regions with a chemistry characteristic of hot gas are
therefore expected to be found, immersed in the interiors of cold atomic
clouds.
We show that the estimated lifetime of the transiently hot regions is long
enough for these specific signatures to develop, locally increasing the
molecular abundances of OH, H_2_O, CH^+^ and HCO^+^ by several orders of
magnitude above those characteristic of the surrounding gas.
The column
densities of species such as CH^+^ and HCO^+^ across a low-density, mostly
atomic, cloud in an active stage of turbulence dissipation are shown to be
comparable to observed values without any fine tuning of parameters.
KEYWORDS: molecular processes, turbulence, ism: general, ism: clouds, ism: kinematics and dynamics, ism: molecules
PERSOKEY:turbulence, ,
CODE: falgarone95a