
%0 Journal Article
%A Gould, RJ 
%T Emission and Absorption of Radio Waves in the Galactic Disk
%J Australian Journal of Physics
%D 1969/04/01
%V 22
%N 2
%P 189-200
%K 
%R https://doi.org/10.1071/PH690189
%U https://www.publish.csiro.au/paper/PH690189 
%X Bremsstrahlung in electron collisions with helium atoms produces up to O' 04 % of the radio emission continuum from the main part of interstellar HII regions, while, near the outer edge where hydrogen is about half-ionized, electron collisions with hydrogen atoms produce up to 2% of the normal electron-proton bremsstrahlung. Radio emission and absorption in electron-hydrogen and electron-helium collisions in HI regions are investigated and found to be negligible at the low temperatures therein. However, low energy cosmic rays may ionize HI regions to a sufficient degree to significantly attenuate radio waves by inverse bremsstrahlung (free-free absorption) in electron-proton Coulomb collisions. Future high resolution surveys of the cosmic radio brightness should be able to distinguish between HI and Ell absorption. 
