This report follows its predecessor in attempting to review significant developments in the field rather than constituting an extensive bibliography. As before, several sections have each been contributed by one author and the President has combined these editorially and attempted to ensure that all major areas have been adequately covered. Thanks are due to individual scientists who responded to requests for information from the authors of sections, to the authors of each section for the care with which they prepared the material, and to Dr. A.N. Simonenko for her help in preparing a summary of recent work in the U.S.S.R. which was of great value in editing the individual sections. As before, references from Astronomy and Astrophysics Abstracts have been used when available.

The scientific interest in Commission 31 topics and their applicability to new and practical fields is exponentially growing, pushing towards the recognition of new problems and subsequent research. In some cases as in Primary Standards the state of the art seems to be rather close to the actual and imagined needs. In other cases as in worldwide precise and accurate synchronization, we have to recognize that we still are far from the goals.

During the period 1 January 1976 to 31 December 1978 the Commission awarded grants to the following eighteen astronomers to enable them to visit institutions in other countries.

The composition of this commission reflects the wide appeal of science history studies and the need for interdisciplinary approach, especially in the studies of ancient and medieval astronomy, where combined scientific, philological and historical competence are necessary conditions. This is why the commission lists over thirty consulting members, historians of science by profession and academic training. The commission is recognized by the IUHPS as a joint commission of both Unions, with a representative of this organization in our Organizing Committee. 69 IAU members, together with the group of consulting members mentioned above, make up for an unusually numerous body. It should be noted that this size is undesirable in some respects and it may call for a general reevaluation.

Commission 46 on Teaching of Astronomy is a Committee of the Executive Committee of the IAU. It was organized thanks to the initiative and great efforts of M.G.J. Minnaert in 196U during the 12th General Assembly of the IAU in Hamburg. Prof. E. Schatzman was the first President of the Commission. Since that time a great deal of work has been accomplished, a large amount of information has been gathered and certain efforts to organize a number of Projects have been made. The experience of the Commission and its Organizing Committee is the most precious result of its work. The benefit to the Commission is the result of hard work of the majority of its members very well known for their activity. Rules and guidelines of operation for Commission 46 were proposed and adopted at the 15th General Assembly of the IAU in Sydney. The main objective of the Commission is to further the development and improvement of astronomical education at all levels throughout the world. But this purpose outlined so generally gives no answer to the question what the Commission should do. The easiest way is in finding some routine and plausible work to accomplish. The results of such work can be immediately materialized in contrast to ideas and pieces of information which require a lot of work to have them brought into life. But in any case the indispensability of Commission 46 is stressed by (i) the increasing importance of astronomy in the world of civilized life and by (ii) contradiction between fundamental importance of astronomy to human progress and its poor representation in the world educational system.

It is now generally recognized that the solar wind represents that part of the solar corona which is not confined by the solar magnetic field, and therefore escapes into interplanetary space. The escaping gas is heated by sources of solar origin (presumably low frequency waves) to about 2 x 106 K within a distance less than (1/20) R from the sun’s surface; although the solar wind temperature decreases thereafter, heating sources may continue to act through 1 a.u. heliocentric distance. A transition from subsonic to supersonic flow occurs within a few solar radii of the sun’s surface, heat conduction representing the principal energy supply for the acceleration of the solar wind. However, additional accelerating processes may also be active.

Whereas the identification of existing or potential observatory sites was an important part of the report for the first three years of existence of Commission 50, during the period 1976-78 the emphasis has been mostly on establishing recommendations for the protection of observing conditions.