Model studying the effect of the solar terminator on the thermospheric parameters

The results of model studying the mechanism of formation of large-scale disturbances in the thermosphere under the action of short-period waves propagating from the middle atmosphere are presented. The region of the solar terminator is considered as a source of such waves. The calculation results for the summer conditions in the Northern Hemisphere indicate that such an energy source, local in the space and time, results in the formation of large-scale inhomogeneities at altitudes of 120–160 km. A disturbance of these inhomogeneities is caused by the nonlinear and dissipative processes accompanying HF propagation in the terminator region. Large-scale disturbances have a quasistationary character and are localized near the morning and evening terminators. Vortex motions around the pole at altitudes of 140–160 km are formed at nigh latitudes of the winter hemisphere under the polar night conditions.