Space plasma is so hot that the atoms break up into charged particles which then become trapped and stored in magnetic fields. When critical conditions are reached the magnetic field breaks up, releasing a large amount of energy and causing dramatic phenomena. The largest space plasma activity events observed in the solar system occur on the Sun, when coronal mass ejections expel several billion tons of plasma mass into space. This book provides a coherent and detailed treatment of the physical background of large plasma eruptions in space. It provides the background necessary for dealing with space plasma activity, and allows the reader to reach a deeper understanding of this fascinating natural event. The book employs both fluid and kinetic models, and discusses the applications to magnetospheric and solar activity. This will form an interesting reference for graduate students and academic researchers in the fields of astrophysics and plasma physics.