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 the earth's magnetosphere to show
how theory and data together form a quantitative framework for
magnetospheric research. We have tried to organize the material along
the philosophy of starting simply and adding com- plexity only as
necessary. We have avoided controversial and relatively new research
topics and have tried to use as examples physical processes generally
accepted as important within the earth's magnetospheric system. However,
even in some of our examples, the question of whether the physical
process applied to a particular problem is the dominant process, has yet
to be answered.