Multi-Constituent Modeling for the Dissipation of Acoustic/Gravity Waves in the Lower Thermosphere

Vertically propagating infrasonic and acoustic-gravity waves generated by transient sources, such as earthquakes, volcanoes, thunderstorms, and rocket launches, can induce fluctuations that are large enough to detectably perturb the upper atmosphere. Fluctuations of neutral species and ionospheric densities caused by wave disturbances are measured in the Ionosphere, Thermosphere, and Mesosphere (ITM region) via remote sensing or GNSS signal perturbations. The evolution of upwardly propagating atmospheric waves and their impact on the ITM region can be simulated via the discretization of the equations of continuum fluid mechanics and subsequent calculations of measurable parameters. Both are challenging due to the range of scales and processes involved. Therefore, an accurate description of wave dynamics and dissipation, and their effects on other constituents, is crucial for capturing the physical processes that influence the behavior and measurability of waves traveling in the ITM. 
In this presentation, an analysis of the dissipative mechanisms that can impact vertically propagating acoustic waves is discussed. The investigation is based on the one-dimensional mass-fraction multi-constituent continuum model proposed by Ern and Giovangigli [https://doi.org/10.1007/978-3-540-48650-3]. Thermal diffusion and mass diffusion induced by temperature and concentration gradients (Soret and Dufour effects) are studied alongside the damping due to thermo-viscous effects for acoustic waves with frequencies <1Hz, similar to those produced by both geophysical and man-made disturbances (earthquakes, explosions, etc). This study's one-dimensional implementation serves as a test bed for higher dimensional models and is intended as a prelude for more comprehensive investigations of the full spectrum of acoustic and gravity waves and their nonlinear evolution in the ITM region. These next steps are discussed.