The magnetotail's role in magnetospheric dynamics: Engine or exhaust pipe

The years 1991–1994 have seen considerable effort to improve on existing substorm models, primarily with the goal to include into the models more of the observed features of substorm dynamics. While a large fraction of the research focused onto local aspects, some significant investigations were also undertaken to place local aspects of substorm dynamics into a more global framework. This report attempts, in an interpretive way, to summarize the results of the latter research, and to point out open questions. The title of the present report raises the question of the importance of the magnetotail in magnetospheric dynamics: The engine, or a mere exhaust. “Engine” is here taken to refer to an energy conversion device, whereas an “exhaust” operates primarily as a drainage channel for all or part of the converted energy. We address this question through the use of research emphasizing energy storage, transport, and dissipation. The report finds that the primary role of the magnetotail is the engine, i.e., the driver, of substorm dynamics. The exhaust pipe function, seen primarily in the ejection of plasmoids, is of secondary importance compared to the major energy transfer and conversion device nessessarily operating in the magnetotail during magnetospheric storms and substorms.