Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization and applications to the Earth and solar atmospheres

Cheremnykh, Oleg K.; Fedorenko, Alla K.; Kryuchkov, Evgen I.; Selivanov, Yuriy A.

The objects of research in this work are evanescent wave modes in a gravitationally stratified atmosphere and their associated pseudo-modes. Whereas the former, according to the dispersion relation, rapidly decrease with distance from a certain surface, the latter, having the same dispersion law, differ from the first by the form of polarization and the nature of decrease from the surface. Within a linear hydrodynamic model, the propagation features of evanescent wave modes in an isothermal atmosphere are studied. Research is carried out for different assumptions about the properties of the disturbances. In this way, a new wave mode – anelastic evanescent wave mode – was discovered that satisfies the dispersion relation inline-formula M1inlinescrollmathml italic ω normal 2 = k x g () italic γ - normal 1 79pt16ptsvg-formulamathimg33f0df67d2ddcade8d0fe7fa1332b131 angeo-37-405-2019-ie00001.svg79pt16ptangeo-37-405-2019-ie00001.png . Also, the possibility of the existence of a pseudo-mode related to it is indicated. The case of two isothermal media differing in temperature at the interface is studied in detail. It is shown that a non-divergent pseudo-mode with a horizontal scale inline-formula M2inlinescrollmathml k x normal 1 / normal 2 H normal 1 57pt14ptsvg-formulamathimg8cedf9d69a25b46d0c88a138a2f21992 angeo-37-405-2019-ie00002.svg57pt14ptangeo-37-405-2019-ie00002.png can be realized on the interface with dispersion inline-formulaω2=kxg. Dispersion relation inline-formula M4inlinescrollmathml italic ω normal 2 = k x g () italic γ - normal 1 79pt16ptsvg-formulamathimgdf435cf2002a50c538fe7255c9641256 angeo-37-405-2019-ie00003.svg79pt16ptangeo-37-405-2019-ie00003.png at the interface of two media is satisfied by the wave mode, which has different types of amplitude versus height dependencies at different horizontal scales inline-formulakx. The applicability of the obtained results to clarify the properties of the inline-formulaf-mode observed on the Sun is analyzed.

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Cheremnykh, Oleg K. / Fedorenko, Alla K. / Kryuchkov, Evgen I. / et al: Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization and applications to the Earth and solar atmospheres. 2019. Copernicus Publications.

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