Relaxation Absorption of Low-Frequency Sound in a Neutral and Partially Ionized Atmospheric Molecular Gas.

The absorption of low-frequency sound in a neutral atmospheric molecular gas and a partially ionized ionospheric molecular plasma is calculated with allowance for both dissipative processes and processes of rotational and vibrational relaxation. At frequencies from 1 to 0. 01 HZ in a neutral atmosphere below 60 km the vibrational relaxation mechanism is found to be of more importance than all the dissipative factors. In a paritally ionized inospheric molecular gas relaxation phenomena are represented by rotational relaxation which constitutes about 30% of the absorption due to viscosity and heat conduction, but in the high-temperature F-region this value increases up to 70-80% (during daytime and during the solar activity maximum).