An important outcome of the workshop will be a book published in the Space Sciences Series of ISSI by Springer. This volume is NOT intended to be the proceedings of the Workshop, but a collection of in-depth papers informed by the contributions and discussions at the Workshop. It should provide a coherent picture of the current state of the subject. All papers will be peer reviewed. The papers will be published both in the hardcover book in this series and also individually in Surveys in Geophysics as they are received. The journal issue and the SSSI volume are expected to appear about 12-18 months after the Workshop.