A Full-Wave Model For a Binary Gas Thermosphere: Effects of Thermal Conductivity and Viscosity

The thermosphere is diffusively separated and behaves as a multiconstituent gas wherein individual species in static equilibrium are each stratified according to their individual scale heights. Gravity waves propagating in the thermosphere cause individual gases to oscillate with different amplitudes and phases. We use a two-gas (N2 and O) full-wave model to examine the roles of thermal conductivity, viscosity, and mutual diffusion on the wave-induced characteristics of both gases. In the lower thermosphere, where the gases are relatively tightly coupled, the major gas (N2) controls the minor gas (O) response. At higher altitudes, the gases become thermally and inertially decoupled, and the wave in each constituent propagates and dissipates consistent with a dispersion relation and vertical scale determined from the constituent scale height. The effects of coupling and diffusion on the relative phases and amplitudes of the fluctuations in each gas are significantly altered by viscosity and thermal conductivity.