Proceedings of the Midnight Sun Conference, held in Tromsø, Norway, July 1-8, 1987

One of the great problems of astrophysics is the unanswered question about the origin and mechanism of chromospheric and coronal heating. Just how these outer stellar envelopes are heated is of fundamental importance, since all stars have hot chromospheric and coronal shells where the temperature rises to millions of degrees, comparable to the temperatures in the stars' cores. Here for the first time is a comprehensive inventory of the proposed chromospheric and coronal heating theories. The proposed heating processes are critically compared, and the observational evidence for the various mechanisms is reviewed. This is essential reading for all those working in such fields as stellar activity, radio and XUV emission, rotation, and mass loss, for whom a detailed and consistent presentation of our knowledge of chromospheric and coronal heating mechanisms is urgently needed.

The original plans for a meeting to celebrate the second centenary of the As tronomical Observatory of Palermo were for a celebration with a double character. The gathering was to have both a historical character, appropriate for a bicenten nial, and a technical character, to note and chronicle the new phase of the history of the Observatory, which has prospered in parallel with the development of this fairly recent topic in astronomical research, the physics of stellar and solar coronae. After the untimely death of the Observatory's Director, Giuseppe S. Vaiana (Pippo to his many friends), a number of colleagues and friends insisted that the celebration should nevertheless be held and should be dedicated to this farsighted scientist who stimulated the development of coronal physics from the early x-ray observations of the solar corona to the recognition of coronae as an observable feature of nearly all stars. This memorial dedication did not change the character of the meeting, which was held in Palermo from 22 to 26 June 1992; as his contributions are very alive in the papers presented at the meeting and collected here, Pippo Vaiana has certainly achieved his place in the history of Astronomy.

An interdisciplinary approach to solar physics, as eighty-nine contributors trace the evolution of the Sun and provide a review of our current understanding of both its structure and its role in the origin and evolution of the solar system.

The International Scientific Spring Meeting of the Astronomische Ge sellschaft (AG) held at Bamberg in April 1991 was devoted to "Vari abilities in Stars and Galaxies". Time-dependent phenomena are observed in a wide range of as tronomical objects. They are caused by different physical mechanisms (for example by pulsation, by accretion, or by dramatic eruptive events in connection with mass outflow) producing observable intensity vari ations through all wavelengths. Many of the papers in this volume are concerned with galactic stars showing such behaviour (for ex ample cataclysmic variables, symbiotic stars, luminous blue variables (LBVs) and novae). Intrinsic variations of the, magnetic field struc ture on observable time scales are, for instance, a peculiarity of cool, solar-like stars and represent a useful tool to study differential rotation and cycles of activity. Recent results on the investigation of gas motions in the inner regions of the Milky Way system, a study of the bipolar galaxy M 82, observations of variable extragalactic radio sources, the variability of emission lines in active galactic nuclei (AGN) as well as continuum variations of quasars and AGN are discussed by several authors. The yearbook series Reviews in Modern Astronomy of the AG to bring the scientific events of the was established in 1988 in order meetings of the society to the attention of the worldwide astronomical community.

concert at Dinkelspiel Auditorium 'An Evening of Songs and Arias' hosted by Dr Kip Cranna of San Francisco Opera, produced and directed by Elizabeth Tucker, and featuring soprano Ellie Holt Murray, mezzo-soprano Marsha Sims; tenor Richard Walker, and baritone David Taft Kekuewa, with piano accompaniment by Mark Haffner, staff coach for San Francisco Opera. Two scientific themes clearly emerged from this conference: (1) the key to progress in flare research lies in a multispectral approach with as much temporal resolution as the photon fluxes allow; and (2) the key to understanding the physics lies in a dynamic interaction between solar and stellar investigations and investigators. During the eight sessions solar and stellar topics were balanced and intermixed in 33 invited and oral presentations. We are particularly pleased that these proceedings will be the springboard to publication of solar-stellar articles in the journal Solar Physics. In addition, 115 very exciting posters were also displayed and a companion volume containing many of these is available as a publication of the Catania Astrophysical Observatory. We dedicate this book to the Solar Maximum Mission and to the Flare Star Consor tium. To all our solar-stellar friends and colleagues: 'Thank you!' BERNHARD M. HAISCH and MARCELLO RODONO 28 March. 1989 AN OVERVIEW OF SOLAR AND STELLAR FLARE RESEARCH BERNHARD M. HAlSCH Div. 91-30. Bldg. 255. Lockheed Palo Alto Research Laboratory. 3251 Hanover St .• Palo Alto. CA 94304. U.S.A.