A review of F region dynamics

The photochemical processes responsible for the formation of the F region of the ionosphere were identified from radio wave reflection and rocket experiments prior to 1960 (for review, see Rishbeth [1967 a ], D. R. Bates [1973, 1974], and Ratcliffe [1974]). It was long recognized that dynamical processes are also extremely important in governing the F layer, but it was not until the decade between 1960 and 1970 that two of the most important processes for setting the plasma in motion horizontally, namely, thermospheric winds and magnetospheric convection, were recognized and confirmed by observation. During the past 4 years, progress in understanding the dynamics of the F layer has largely been made through experimental measurements that have provided detailed information on these two phenomena. On the theoretical side, there have been considerable advances in developing time‐dependent computer models of the F region which incorporate the photochemical processes, the thermal structure, and the transport arising as a result of neutral winds in an internally self‐consistent manner. These permit one to test the relative importance of various phenomena in contributing to the observed behavior and estimating the magnitude of some parameters which remain poorly known. There have also been important developments in understanding the phenomenon of the escape of plasma at high latitudes into field tubes that have been emptied of ionization; however, many of these ideas still await experimental confirmation.