The phenomena of space physics are complex and their understanding often requires the integration of different concepts. To help the beginner, this book uses a new methodological approach. The first chapters introduce simple concepts of plasma physics and describe where these can be applied in space physics. Subsequent chapters are devoted to more complex observations, interpreted in terms of the concepts introduced earlier. New, more difficult, concepts are introduced as they are required. Thus observations and physical concepts are interwoven to give basic explanations of phenomena and also show the limitations in these explanations and identify some fundamental questions. This second edition has been updated and extended. Improvements include: the use of SI units; addition of recent results from SOHO and Ulysses; improved treatment of the magnetosphere as a dynamic phenomenon; text restructured to provide a closer coupling between basic physical concepts and observed complex phenomena.