The aim of the VIRGO investigation (Variability of solar IRradiance and Gravity Oscillations) on SOHO (SOlar and Heliospheric Observatory) is to determine the characteristics of pressure and internal gravity oscillations by observing irradiance and radiance variations, to measure the solar total and spectral irradiance and to quantify their variability over periods of days to the duration of the mission. VIRGO contains two different active-cavity radiometers for monitoring the sol- ar 'constant' (DIARAD and PM06-V), two three-channel sunphotometers (SPM) for the measurement of the spectral irradiance at 402, 500, and 862 nm with a bandwidth of 5 nm, and a low-resolution imager (Luminosity Oscillation Imager, LOI) with 12 'scientific' and 4 guiding pixels, for measuring the radiance dis- tribution over the solar disk: at 500 nm. The instrumentation has been described in detail by Frohlich et al. (1995). In addition, the observed in-flight performance and operational aspects of the irradiance observations are described by Frohlich et al. (1997), and those of the LOI by Appourchaux et al. (1997).

This book focuses on the recent advances in our understanding of solar convection and activity, and on new methods and results of helioseismic diagnostics. It provides a comprehensive overview of the current status of the field and presents new ideas and approaches.

This is an exhaustive survey of present-day solar research including both theory and observations. It deals with eruptive flares, filament eruption in x-rays and radio waves, energy release and transport, and terrestrial response to solar flares. Details of the most recent SOLAR-A project (launched shortly after the conference) are also presented.

The Solar and Heliospheric Observatory (SOHO) is a joint ESA/NASA mission to study the Sun, from its deep core to the outer corona, and the solar wind. SOHO was launched on 2 December 1995 and was inserted into a halo orbit around the L1 Lagrangian point on 14 February 1996. From this vantage point it is continuously monitoring the Sun, the heliosphere, and the solar wind particles that stream toward the Earth. Nominal operations of the SOHO mission started in April 1996 after commissioning of the spacecraft and the scientific payload. Detailed descriptions of the twelve instruments, which represent the most comprehensive set of solar and heliospheric instruments ever developed and placed on the same platform, can be found in "The SOHO" "Mission" ("Solar Physics," Vol. 162, Nos. 1-2, 1995).
This volume contains papers reporting the first scientific results from the SOHO mission as well as descriptions of the in-flight performance of some of the instruments, published in two parts of a "Solar Physics" special (Part I in "Solar Physics," Vol. 170, No. 1; Part II in "Solar Physics," Vol. 175, No. 2). Unique data from the three helioseismology instruments (GOLF, VIRGO, MDI/SOI) provide new insights into the structure and dynamics of the solar interior, from the deep core to the outermost layers of the convection zone. The remote sensing instruments (SUMER, CDS, EIT, LASCO, UVCS, SWAN) present exciting new data on a wide range of topics such as transition region dynamics, coronal plumes, coronal holes, streamers, and coronal mass ejections, giving us our first comprehensive view of the outer solar atmosphere and corona. These data are complemented by energetic particle measurements produced by the ERNE instrument on board SOHO.

This book focuses on the recent advances in our understanding of solar convection and activity, and on new methods and results of helioseismic diagnostics. It provides a comprehensive overview of the current status of the field and presents new ideas and approaches.

This Catalog originated as a common enterprise of solar physicists and space scientists under the auspices of the Second Working Group of the Inter-Union Commission of Solar Terrestrial Physics (IUCSTP). It is a pleasure to acknowledge the support we received from the IUCSTP president, Dr H. Friedman, and the IUCSTPSecretary, Dr E. R. Dyer during the several years we have spent on this project. The aim of our work has been to assemble all observations of particle events from the first PCA observation in 1955 through two solar cycle maxima up to the end of 1969, in order to preserve these data from the first epoch of the space era in a concise form for use in the future. Because the techniques of observation have very much improved in the present solar cycle, there is a tendency to consider the observations before 1964 as incomplete and out-of-date; one must not forget, however, that the 19th solar cycle greatly differed from cycle No. 20 in the level of its activity, and also may have been the last cycle of strong activity for many decades to come. Therefore, the particle event observations before 1964 'should be compiled in a consistent manner for comparison with later observations, and we believe that the Catalog achieves this. The rapid development of the exploration techniques necessarily results in a significant amount of inhomogeneity in the Catalog, as increasingly smaller events were detected.

This book is the first part of the originally planned publication by Z. Svestka and L. D. de Feiter 'Solar High Energy Photon and Particle Emission'. The second part, with the original title, was to be published by de Feiter in about one year from now. However, to the deep sorrow of all of us, Dr de Feiter died suddenly and unexpectedly when the present book was in print. Thus, unfortunately, de Feiter's second part may not appear. Due to the fact that the originally planned publication was divided into two parts, the present book is mainly descriptive and concerned with the flare morphology. It was expected that theoretical interpretations would be extensively developed in the second part, prepared by de Feiter. In particular, this refers to the theoretical back grounds of radio emissions, particle acceleration and particle propagation in space. Only in Chapter II, concerning the 'low-temperature' flare, do we go deeper into the theoretical interpretations, anticipating that de Feiter would have been concerned mainly with the 'high-energy' physics. Still, the book includes discussions on all important aspects of flares and thus can present the reader with a complete picture of the complex flare phenomenon. It is clear that many observed data on flares can be interpreted in different ways."