At its Liège meeting, in July 1963, the Executive Committee of the Union voted to hold this Joint Discussion as a small homage to the memory of Professor Struve. I do not need to stress why the subject of ‘Close Binaries’ was chosen as we all know that it was closer to Professor Struve’s heart than any of the other ones in which he divided his broad astronomical interest.

Mrs Mary Struve has written to me the kind letter I am going to read, a letter which summarizes so clearly how much Professor Struve would have appreciated this kind of homage.

At its Liège meeting, in July 1963, the Executive Committee of the Union voted to hold this Joint Discussion as a small homage to the memory of Professor Struve. I do not need to stress why the subject of ‘Close Binaries’ was chosen as we all know that it was closer to Professor Struve’s heart than any of the other ones in which he divided his broad astronomical interest.

Mrs Mary Struve has written to me the kind letter I am going to read, a letter which summarizes so clearly how much Professor Struve would have appreciated this kind of homage.

The discovery of oscillatory motion in the solar photosphere and of the ‘super-granulation’ in the chromosphere has changed our ideas about the hydrodynamics of the solar atmosphere considerably. In this Joint Discussion we shall mainly consider the theoretical implications of this change. As the ultimate aim is an understanding of the hydrodynamics in all stellar atmospheres—not only in the Sun, some discussion of other stellar atmospheres will be included.

The discovery of oscillatory motion in the solar photosphere and of the ‘super-granulation’ in the chromosphere has changed our ideas about the hydrodynamics of the solar atmosphere considerably. In this Joint Discussion we shall mainly consider the theoretical implications of this change. As the ultimate aim is an understanding of the hydrodynamics in all stellar atmospheres—not only in the Sun, some discussion of other stellar atmospheres will be included.

The discovery of oscillatory motion in the solar photosphere and of the ‘super-granulation’ in the chromosphere has changed our ideas about the hydrodynamics of the solar atmosphere considerably. In this Joint Discussion we shall mainly consider the theoretical implications of this change. As the ultimate aim is an understanding of the hydrodynamics in all stellar atmospheres—not only in the Sun, some discussion of other stellar atmospheres will be included.