Magnetosphere‐ionosphere coupling: Contributions from IMS satellite observations

Abstract

This paper provides a preliminary review of International Magnetospheric Study (IMS) period advances in our understanding of how the magnetosphere and ionosphere act as an electrically coupled system. Emphasis is placed on particle and electric field observations from the AE, S3‐2, S3‐3, and DMSP satellites. Field‐aligned current measurements are reviewed by Saflekos and co‐workers. An overview of pre‐IMS measurements provides the point of departure. The capabilities of the various satellite instrumentation packages are then critically summarized. Measurements are divided according to their auroral oval or polar cap origins. The systematics of auroral boundary variations, large‐scale precipitation, and subauroral rapid convection are discussed with reference to their magnetospheric sources. The wave, electric field, and particle environment of inverted‐V structures have been given detailed study during IMS. The direct observation of parallel electric fields that accelerate electrons earthward to form discrete arcs and ion beams upward into the magnetosphere is a contribution whose analysis will continue strongly into the post‐IMS period. Studies of satellite measurements show that the cross‐polar cap potential is quantifiably related to solar wind/IMF parameters. The detection of sun‐aligned arcs as well as extensive regions of sunward convection in the polar cap suggests that the magnetosphere/solar wind coupling is radically different during periods of northward and southward IMF orientations.