Christopher T. Russell has written over 1500 articles in books and journals on planetary and space physics and has been cited over 45,000 times. He has been awarded the AGU's Macelwane medal, its Fleming medal and COSPAR's Science award. He has been a principal investigator on numerous missions including ISEE 1 and 2, Pioneer Venus, the ISTP/Polar mission and the Magnetospheric Multiscale mission. He is also the Principal Investigator of the ion-propelled Dawn Discovery mission to the asteroid belt. Janet G. Luhmann has authored or co-authored over 600 publications in areas of space and planetary physics and served as Senior Editor for the Journal of Geophysical Research, Space Physics. She has been awarded AGU's Fleming medal and COSPAR's Science award. She has been an Investigator on numerous NASA and NSF projects involving the Sun's control of the space environments of the Earth and planets, most recently the STEREO mission to observe the 3D effects of solar activity in the inner solar system, and the MAVEN mission to study Mars atmosphere escape to space. Robert J. Strangeway is an author or co-author on over 200 publications covering a variety of space physics topics. He regularly teaches the Introduction to Space Physics course at the University of California, Los Angeles, which is the basis for this book. He is currently the Senior Editor for the Journal of Atmospheric and Solar-Terrestrial Physics. In addition to serving as an Investigator with the missions AMPTE/CCE, Pioneer Venus and FAST he was the Principal Investigator for the magnetometers developed for Space Technology 5.