I would like to thank the editors of Living Reviews in Solar Physics for the invitation to prepare this review. I gratefully acknowledge John Kohl, Adriaan van Ballegooijen, Leonard Strachan, John Raymond, William Matthaeus, Philip Isenberg, Joseph Hollweg, S. Peter Gary, Eckart Marsch, Marco Velli, Mari Paz Miralles, Larry Gardner, and Enrico Landi for many valuable discussions and collaborations. I would especially like to thank the colleagues with whom I have engaged in more adversarial debates over the years, such as Ian Axford, Chuanyi Tu, Nathan Schwadron, and Nour-Eddine Raouafi. “As brothers fight ye!”
This work was supported by the National Aeronautics and Space Administration (NASA) under grants NNG04GE77G, NNX06AG95G, NNX07AL72G, and NNX09AB27G to the Smithsonian Astrophysical Observatory. SOHO is a project of international cooperation between ESA and NASA. This research made extensive use of NASA’s Astrophysics Data System (ADS) and the John G. Wolbach Library at the Harvard-Smithsonian Center for Astrophysics.
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