From 17 to 21 April 1967 a Study Week was held in the hotel 'De Bilderberg' near Arnhem, Holland, with the purpose to establish a new, and if possible, generally acceptable working model for the quiet parts of the solar photosphere and low chromosphere. The organizers of the conference hoped that even if this latter goal appeared too far to be reached, such a meeting would still be useful, if only for enumerating the crucial problems in solar photospheric research, and for defining future subjects of research. About twenty solar physicists from outside the Netherlands participated in the Study Week, while some others, though prevented from actively attending, sub mitted their comments before the meeting. The two above-mentioned goals were reached: a working model could be estab lished; yet it became clear that not everyone would agree about this model, and it became obvious too that future research is strongly needed, in particular in the field of line formation (coherence, or non-coherence; local thermal equilibrium), while also the motion field of the photosphere and chromosphere is insufficiently known, and its influence on the formation of spectral lines hardly understood.

Solar and stellar photospheres constitute the layers most accessible to observations, forming the interface between the interior and the outside of the stars. The solar atmosphere is a rich physics laboratory, in which the whole spectrum of radiative, dynamical, and magnetic processes that tranfer energy into space can be observed. As the fundamental processes take place on very small spatial scales, we need high· resolution observations to explore them. On the other hand the small-scale processes act together to form global properties of the sun, which have their origins in the solar interior. The rapid advances in observational techniques and theoreticallllodelling over the past decade made it very timely to bring together scientists from east and west to the first lAU Symposium on this topic. The physics of the photosphere involves complicated interactions between magnetic fields, convection, waves, and radiation. During the past decade our understanding of these gener ally small-scale structures and processes has been dramatically advanced. New instrumen tations, on ground and in space, have given us new means to study the granular convection. Diagnostic methods in Stokes polarimetry have allowed us to go beyond the limitations of spatial resolution to explore the structure and dynamics of the subarcsec magnetic struc tures. Extensive numerical simulations of the interaction between convection and magnetic fields using powerful supercomputers are providing deepened physical insight. Granulation, magnetic fields, and dynamo processes are being explored in the photospheres of other stars, guided by our improved understanding of the solar photosphere.

The widespread tendency in solar physics to divide the solar atmosphere into separate layers and to distinguish phenomena of solar activity from phenomena of the quiet Sun emphasizes the wide ranging diversity of physical conditions and events occurring in the solar atmosphere. This diversity spans the range from a neutral, essentially quiescent atmosphere to a highly ionized, violently convective atmosphere; from a domain in which magnetic field effects are unimportant to a domain in which the magnetic pressure exceeds the gas pressure, and from a domain in which the particle motions are Maxwellian to a domain in which an appreciable fraction of the particles is accelerated to relativistic energies. It is now widely recognized that the chromosphere and corona have a common origin in the mechanical energy flux generated in the hydrogen convection zone lying beneath the photosphere. Furthermore, magnetic field phenomena appear to be as vital to the structure of th~ quiet Sun as to the active Sun. For these reasons it appears desirable to present a unified treatment of the entire solar atmosphere, both active and quiet, in a single volume. On the other hand, such a treatise must be very long if it is to avoid being superficial, and it is very difficult for a single author to write authoritatively on such a wide range of topics.

The COSPAR Colloquium on Solar-Terrestrial Magnetic Activity and Space Environment (STMASE) was held in the National Astronomy Observatories of Chinese Academy of Sciences (NAOC) in Beijing, China in September 10-12, 2001. The meeting was focused on five areas of the solar-terrestrial magnetic activity and space environment studies, including study on solar surface magnetism; solar magnetic activity, dynamical response of the heliosphere; space weather prediction; and space environment exploration and monitoring. A hot topic of space research, CMEs, which are widely believed to be the most important phenomenon of the space environment, is discussed in many papers. Other papers show results of observational and theoretical studies toward better understanding of the complicated image of the magnetic coupling between the Sun and the Earth, although little is still known little its physical background. Space weather prediction, which is very important for a modern society expanding into out-space, is another hot topic of space research. However, a long way is still to go to predict exactly when and where a disaster will happen in the space. In that sense, there is much to do for space environment exploration and monitoring. The manuscripts submitted to this Monograph are divided into the following parts: (1) solar surface magnetism, (2) solar magnetic activity, (3) dynamical response of the heliosphere, (4) space environment exploration and monitoring; and (5) space weather prediction. Papers presented in this meeting but not submitted to this Monograph are listed by title as unpublished papers at the end of this book.