This reprint of the second edition includes a new chapter--Space Weather Services. The purpose of this chapter is to define space weather nowcast and forecast requirements for the commercial space weather community. A nowcast is a short-range forecast usually on the order of 1 or 2 hours lead tie. This is the only textbook on the space environment written for the novice which covers all the major topics in space physics. The reader is expected to have a solid background in introductory physics; therefore, this edition is most useful as a text for senior-year college or first-year graduate students. Topics include plasma physics, solar physics, solar wind processes, geomagnetism, magnetospheric physics, physics of the neutral atmosphere, ionospheric physics, ionospheric variability, radiowave propagation in the ionosphere, and space environmental effects on spacecraft.