This report originated in 1999 as a result of discussions between the Committee on Solar and Space Physics (CSSP) and officials within NASA’s Office of Space Science Sun- Earth Connections program. As noted in the statement of task (Appendix A), the objective of the study was to provide a scientific assessment and strategy for the study of magnetized plasmas in the solar system. By emphasizing the connections between locally occurring (solar system) structures and processes and their astrophysical counterparts, the study would contribute to a unified view of cosmic plasma behavior. An additional objective was to relate basic scientific studies of plasmas to studies of the Sun’s influence.