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In this study, numerical simulations of planetary‐scale waves (PSWs), generated in the troposphere, were performed for altitudes from the Earth's surface up to 300 km. The influence of thermospheric effects of solar activity (SA) on the amplitudes and phases of westward traveling PSWs with zonal wave numbers 1 and 2 and periods 4–16 days propagating from the troposphere was simulated. Such simulations for a large number of PSW modes in the thermosphere were made for the first time. The effects of SA changes at altitudes above 100 km were involved in the general circulation model MUAM. The ionospheric conductivities for minimum and maximum SA levels were included into the MUAM. The simulation results were averaged over two ensembles of model runs with different PSW phases for conditions corresponding to the high and low SA levels for January–February. PSW atmospheric refractivity index and Eliassen‐Palm flux were calculated. They correspond to simulated changes in PSW amplitudes. Changes in the zonal velocity and temperature caused by the SA variations can modify spatial distributions of the westward traveling PSWs. Wave amplitudes significantly (up to 100%) decrease at the thermospheric heights under high SA, which is accompanied by decreasing vertical component of the Eliassen‐Palm flux. The 7‐, 10‐, and 16‐day PSWs could have larger partial reflection and worse propagation conditions than the 4‐ and 5‐day waves in the Southern Hemisphere under the high SA. At altitudes below 100 km, minor differences in zonal velocity and PSW amplitudes between high and low SA are found.

One of the important features of the middle atmosphere dynamics is the quasi-biennial oscillation (QBO) of zonal mean flows at stratospheric heights (e.g., Baldwin et al., 2001;Holton & Tan, 1980). This phenomenon is observed at equatorial latitudes: the direction of the zonal wind changes to the opposite with the period varying between 22 and 34 months. The highest zonal wind velocities are observed at altitudes of 20-30 km: about 20 m/s for westerlies and about 30 m/s for easterlies (Baldwin et al., 2001). Although the QBO is a dynamic process occurring in the stratosphere in the vicinity of the equator, its influence in the form of a quasi-2-year periodicity is observed in the composition of the atmosphere and in hydrodynamic fields at other latitudes and altitudes. For instance, Holton and Tan (1980) analyzed the response of the extratropical circulation to the QBO and showed that it is particularly strong during northern winter, where the zonal mean westerly jet is weaker during the easterly QBO phase (eQBO) than that during the westerly QBO phase (wQBO). Garfinkel et al. ( 2012) concluded that the QBO effect at high latitudes might be related to the induced changes in the thermally balanced subtropical jet and in the associated changes in the refractive index, which restricts the propagation of transient Rossby waves into the subtropics enhancing transient wave activity and the meridional mass circulation. In addition, as it was shown by Cnossen and Lu (2011), QBO interacts with variations caused by the 11-year solar cycle. Gavrilov et al. (2015) studied peculiarities of planetary wave (PW) and orographic gravity wave (OGW) interactions in the middle and upper atmosphere under different QBO phases. They showed that transitions from eQBO to wQBO can cause PW amplitude changes up to ±(30-90)% at middle and high northern latitudes. According to Koval et al. (2018), variations of PW amplitudes may occur due to nonlinear interactions between PW modes and changes in the global circulation under different QBO phases, which produce changes in the refractivity indices and EP fluxes for PW modes. Recently, studies dedicated to the research of the influence of the QBO phases on the transport of greenhouse gases have become especially relevant (Gabriel, 2019). In particular, the numerical simulation was used to reveal the long-term changes in northern midwinter temperature, zonal wind, and residual circulation, that are much stronger during wQBO than during eQBO. Among the other important