Influence of Solar Activity on Penetration of Traveling Planetary‐Scale Waves From the Troposphere Into the Thermosphere

Abstract

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.

QBO, ENSO, and Solar Cycle Effects in Short‐Term Nonmigrating Tidal Variability on Planetary Wave Timescales From SABER—An Information‐Theoretic Approach

“…The solar cycle dependence of traveling planetary waves is a comparatively understudied field, mainly due to the challenge of obtaining homogeneous measurements on decadal time scales. The few previous studies either focused on the thermosphere/ionosphere, where the wave amplitudes are dominated by the temperature dependence of dissipative processes in the E‐region and tidal‐planetary wave interactions to imprint the planetary wave periods on this altitude regime (e.g., Forbes et al, 2018; Koval et al, 2018), or long‐term radar observations in the mesosphere. The former do not matter for the current question, and the latter are largely focused on the quasi‐2‐day wave (Q2DW) ranging from no correlation at northern midlatitudes (Lilienthal & Jacobi, 2015), to large positive correlation in the meridional wind but negative correlation with the zonal wind at subtropical NH latitudes (Gu et al, 2013), to small negative correlations at the equator (Rao et al, 2017).…”

A Statistical Analysis of the Propagating Quasi 16‐Day Waves at High Latitudes and Their Response to Sudden Stratospheric Warmings From 2005 to 2018

“…They suggested that the PWs play an important role in the displacement of the SSW. Many studies have used the EP flux to reveal the magnitude and direction of the energy propagation caused by the PWs (Chen & Huang, ; Harada et al, ; Huang et al, ; Koval et al, ; Leroy & Anderson, ; Portafaix et al, ). The composite EP flux of the quasi 16‐day waves with different wavenumbers at 10 hPa is calculated.…”

Quasi‐6‐Day Wave Effects on the Equatorial Ionization Anomaly Over a Solar Cycle

“…Main characteristics of the Q6DW, including its latitude/height structure and intra‐annual/interannual variability, are well described in the studies mentioned above. Also, general circulation models have been used to examine the excitation and propagation mechanisms of the Q6DW (Liu et al, ; Miyoshi, ; Miyoshi & Hirooka, ) and to quantify the impact on the upper atmosphere (Forbes, Maute, et al, ; Forbes, Zhang, et al, , Gan et al, , ; Koval et al, ; Pedatella et al, ).…”

“…In a follow‐up study (Forbes, Maute, et al, ), they demonstrated that much of planetary wave variability in the ionosphere occurs as a result of such interaction between planetary waves and tides. Koval et al (), also using a numerical model, showed that the vertical extent of westward traveling planetary waves, including the Q6DW, depends on solar activity. They found that planetary wave amplitudes in the thermosphere above 100 km are larger when the solar flux is lower.…”