Dynamical coupling processes between the middle atmosphere and lower ionosphere

A variety of dynamical processes are important in coupling motions within the middle atmosphere and lower ionosphere. These processes can generally be classified as either advective, wave-like or diffusive. Within the middle atmosphere, wave-like processes, and especially gravity waves, are of crucial importance. Turbulent diffusion and advection probably play lesser, but not insignificant, roles. However, whether these same concepts apply to coupling for regions outside the middle atmosphere—and especially between the upper middle atmosphere and the lower ionosphere—is not clear. In this paper the current knowledge about coupling processes between these important regions is reviewed. We discuss coupling processes in the middle atmosphere with the objective of examining how well these concepts may be extended to the topic of middle atmosphere to ionosphere coupling. Different approaches to understanding, and the different experimental procedures used by workers studying the middle atmosphere and ionosphere, also make comparisons difficult. The importance of the measurement of common parameters is highlighted, and the need for coordinated campaigns to examine the interactions between the regions is emphasized.