Model Study of the Response of the Thermosphere to Perturbations of Mesospheric Tides and Planetary Waves during a Sudden Stratospheric Warming

The results of numerical simulations of the effects of a sudden stratospheric warming (SSW) in January 2009 are examined. The calculations are performed within the framework of the Global Self-Consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP), which calculates the parameters of the neutral and charged components of the upper atmosphere. An analysis of the numerical simulation results showed that the perturbation of mesospheric tidal and planetary waves significantly affects the structure of variations of the thermosphere at altitudes below 150 km. At higher altitudes, the characteristics of planetary and tidal waves in the thermosphere are practically insensitive to the corresponding mesospheric perturbations. The calculated space-time structure of ionospheric perturbations caused by mesospheric and planetary tidal waves is in qualitative agreement with observation data. The results show that the main reason for the observed ionospheric effects is the perturbation of the electric fields in the dynamo region. However, the calculated magnitudes of the ionospheric effects produced by the SSW are at least two-to threefold weaker than the observed. It is assumed that, in order to achieve a quantitative agreement between simulation and experimental results on the ionospheric effects of the SSW, it is not enough to consider only the dynamics of planetary and tidal waves in the mesosphere. An additional source of the perturbation of the thermosphere and ionosphere during the SSW may be associated with the propagation of internal gravity waves from the lower atmosphere and their dissipation in the thermosphere.