These proceedings are based upon in~roductory talks, re- search repor~s and discussions at the NATO Advanced Work- shop on ELECTROMAGNETIC COUPLING IN THE POLAR CLEFTS AND CAPS, held at Lillehammer, Norway, 20-24th September 1988. By this book we will make the information which was pro- vided to the participants of the workshop, accessible to a wider audience. Electromagnetic processes governing particle, momen- tum, and energy transfer from the solar wind via the magne- tosphere and into the earth's upper atmosphere are the main topics of solar-terrestrial research. Due to the peculiar magnetic field configuration in the magnetosphere, result- ing from the interaction with the shocked solar wind, the sunward-side boundary is mapped along magnetic field lines in~o a thin, arc-like band of the days ide polar ionosphere at the boundary of the polar cap; i.e. ~he ionospheric cleft region. The polar cusp is a separate, more limited region near magnetic noon, as defined by electron and proton precipitation detected from polar orbiting satel- lites. The basic physics of the different coupling modes at the dayside magnetopause is a matter of great controversy. This is an important problem to solve, also because similar boundaries exist in stellar objects throughout the Uni- verse. It is expected that ground-based remote sensing tech- niques, with their ability to continuously monitoring the temporal and spatial variations of the ionospheric signa- tures, will have a great impact on this problem, in parti- cular when combined with in situ measurements.

`The book seems absolutely necessary for someone working in this field, including students. Workers in other fields of space plasmas, plasma astrophysics or planetary science would also profit some by learning about so many different aspects of electromagnetic coupling.'
Solar Physics, 131, 1991