Physical processes in the interstellar matter determining parameters of radio recombination lines in meter and decameter ranges

Abstract

AbstractWe give a review of problems connected with the interpretation of meter and decameter carbon radiolines. The lines are formed inside clumps of molecular clouds in layers with a column density N ≈ 6 · 1021 cm−2. These clumps are very typical structures. The distribution of physical parameters (number density, temperature, etc.) inside the clumps is poorly known. The most difficult and important question is the penetration of subcosmic rays into the clumps. Observations show that the ionization rate is ζ = (1–7) · 10−17 s−1 inside molecular clouds and significantly greater in the diffuse gas. Long‐wave radio recombination lines can probably be used for the analysis of the distribution of subcosmic rays inside molecular clouds. The interpretation is complicated by the influence of low‐temperature dielectron recombination and poorl known variations of carbon depletion in the clumps.