Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 54. Science involves a well orchestrated interplay between theory and experiment. Past unexplained observations suggest new questions to be asked, and answering these questions many times requires new observational techniques or at least new applications of old techniques. Solar system plasma physics is a classic example of the scientific process at work and has benefited from the rapid technological exploration of our near space environment over the last 35 years. This book is a 1988 snapshot of the scientific process in solar system plasma physics. It is structured by a series of scientific questions. Under each of these headings are theoretical papers which review the pertinent science and properly formulate the question in specific observational terms. These are followed by experimental papers which address the present state of observational techniques which can be used to investigate these outstanding problems. In addition, two introductory papers offer overviews of the fields of solar physics and magnetospheric physics; each addresses itself, as a kind of short course in its respective discipline, to scientists from the other discipline.