The history of modern helioseismology is only ten years old. In 1975 F-L Deubner separated for the first time the spatial and temporal pro perties of the solar five-minute oscillations, and was thus able to measure the dispersion relation for high-degree acoustic modes (p modes). The diagnostic value of these observations was appreciated immediately. Indeed, by comparing the observed relation with computations that had already been carried out by R.K. Ulrich, and subsequently by H. Ando and Y. Osaki, it was recognised that contemporary solar models that had been constructed with the low observed neutrino flux in mind were too hot in their outer layers. Moreover, their convection zones were too shallow. Since that time the observations have improved. There is now good reason to suppose that a sufficiently careful analysis will lead to a direct determination of the helium abundance in the solar convection zone, especially when foreseeable further improvements in the observations have been achieved. The data will also provide useful diagnostics of the uncertain equation of state of partially ionized plasmas, and they might also enable us to measure the large-scale structure of the convec tive flow.

" ... Concise explanations and descriptions - easily read and readily understood - of what we know of the chain of events and processes that connect the Sun to the Earth, with special emphasis on space weather and Sun-Climate."--Dear Reader.

Pulsating and eccentric binary stars play a fundamentally important role in deciphering the mass distribution within stars. The present volume reviews the fundamental concepts of both radial and nonradial oscillations in the stars, including the Sun. Helio- and astroseismological results are reviewed, from the basics to the most recent developments. A new theory is presented, which seems to explain the mechanism of the light and radial velocity variations of recently discovered Ap stars. This textbook covers almost all kinds of variable stars of widely different characteristics. It will serve as a reference text for a very long time to come, not only for specialists but also for undergraduate students of physics and astronomy.

Proceedings of the 121st Colloquium of the International Astronomical Union, held at Versailles, France, May 22-26, 1989