Studies of ionospheric plasma and electrodynamics and their application to ionosphere‐magnetosphere coupling

A brief description of the contributions of the Dynamics Explorer (DE) program to an understanding of ionospheric plasma dynamics is given. In addition to being used in some further study of small‐scale structure in the equatorial ionospheric number density, the DE 2 intrumentation has been extensively used to study the bulk motion of the plasma in the equatorial ionosphere. Variations in the east‐west plasma drift, at night as a function of magnetic flux tube apex height, show a decrease in magnitude with increasing height above the altitude of the peak F region concentration. The role of both E region and F region winds in producing this behavior and the differences between DE measurements taken at solar maximum and similar observations at solar minimum have been discussed. The work described here shows a general convergence of opinion about the behavior of the ionospheric convection pattern at high latitudes during periods of southward interplanetary magnetic field (IMF). Progress has been made in describing the magnetosphere‐solar wind interaction that may be involved in the production of the convection pattern. In particular, the expected magnetic field topology and the applicability of different convection drivers have been examined. The characteristics of the high‐latitude ionospheric plasma motion during periods of northward IMF have been extensively studied. Under such conditions the existence of small‐scale (1–10 km) and medium‐scale (10–200 km) structures in the electric field and plasma motion is quite evident. Its relationship to auroral forms and in particular to the theta aurora has been examined in some detail. The interpretation of larger‐scale electric field and plasma drift features in terms of closed loop convection trajectories and the applicability of different theoretical models to the data have also been discussed.