The upper atmosphere in motion

Abstract The atmosphere above 80 km exhibits a wide range of dynamical phenomena. These are largely hydrodynamic in nature, and their sources of energy are likely to lie principally at lower levels. The regions are ionized, however, and hydromagnetically controlled motions also exist. They are generated from above as well as below. The observational evidence is reviewed broadly here, in groupings determined by the physical processes that are thought to be operative, and the corresponding theories are measured against it. Many shortcomings are disclosed and assessed, and profitable avenues for future research are tentatively explored. Several areas are indicated in which the dynamical processes modify other features of the upper atmosphere, but these are not analysed in detail.