The discovery of the earth's radiation belts in 1957 marked the beginning of what is now known as magnetospheric physics. The field has evolved normally from an early discovery phase through a period of exploration and into an era of quantitative studies of the dynamics of magnetized plasmas as they occur in nature. Such environments are common throughout the universe and have been studied in varying detail at the sun, the planets, pulsars, and certain radio galaxies. The purpose of this book is to describe basic quantitative aspects of magnetospheric physics. We use selected examples from...