A major motivation for writing this book is the strong fascination that visible signatures of plasma activity are able to generate. This goes along with considerable professional research interest in this area. Also, those who have admired spectacular pictures or video presentations on the internet displaying spacecraft observations of auroral activity or of solar eruptions, are often motivated to learn more about their physical background.

In the early days of spacecraft observations, the understanding of dynamical phenomena such as geomagnetic storms and solar flares was considered as poor and high up on the list of particularly challenging problems. Remarkably, this is still true today. The observational database has increased dramatically and important new phenomena were discovered, such as coronal mass ejections and manifestations of the global nature of magnetospheric substorms involving large regions of the magnetosphere. There are many more aspects than envisaged originally, and today we have good reasons to use the comprehensive notions of solar and magnetospheric activity, which in this book are combined under the working term space plasma activity. The desire to understand these complex phenomena has mobilized considerable research efforts, but due to the overwhelming complexity that one encounters, our present understanding is still far from being satisfactory.

One might ask, whether in this situation it is appropriate to write a book that concentrates on space plasma activity.