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Our first attempt to organize a Symposium on solar activity was made at the lAO General Assembly in Brighton 1970. There, at the session of Commission 10, we proposed to organize a Symposium which would stress the observational aspects of solar activity. It was our hope that such a Symposium might stimulate studies of those important problems in solar physics which for a long time had been neglected in overall scientific discussion. Although a provisional date for the Symposium was then decided, it did not take place to avoid overlapping with other lAO activities. At the session of Commission 10 in Sydney -on the occasion of the XVth lAO General Assembly in 1973 -we repeated our proposal and forwarded the invitation of the Czechoslovak Academy of Sciences to organize the Symposium in Prague. Both were accepted. During the discussions about the programme of the Symposium -enthusiastically promoted by the late president of Commission 10, Prof. K. O. Kiepenheuer -it was decided to change slightly its subject. The theoreti cal problems were stressed and the majority of the Scientific Organizing Committee agreed not to deal with short-lived phenomena of the solar activity or with individual active regions. Symposium No. 71 was held in Prague from August 25 to August 29, 1975. Its Organizing Committee consisted of V. Bumba (Chairman), W. Deinzer, R. G. Giovanelli, R. Howard, K. O. Kiepenheuer, M. Kopecky, T. Krause, M. Kuperus, G.
List of contents
The Enigma of Solar Activity.- 1/Basic Observed Parameters of the Solar Cycle.- Differential Rotation and Global-Scale Velocity Fields.- Differential Rotation and Giant Cell Circulation of the Solar Ca+-Network.- Rotational Characteristics of Coronal Holes.- On Differences in Differential Rotation.- Large-Scale Solar Magnetic Fields.- Small-Scale Solar Magnetic Fields.- Investigation of Coronal Rotation by the Spectroscopic Method.- Fast Variations of the Solar Rotation.- About the Relation between the Limb Effect of the Redshift on the Sun and the Large-Scale Distribution of Solar Activity.- Drift of Sunspots in Latitude.- Velocities Observed in Supergranules.- Long Term Evolution of Solar Sector Structure.- Solar Cycle Evolution of the General Magnetic Field.- Coronal Bright Points.- Cyclical and Secular Variations of Solar Activity.- Some Results of the Space Distribution of the Activation Vector of the Filaments in the 11-year Cycle.- Sequences of Large Sunspot Groups.- Characteristic Features of Cyclic Change of Solar Activity after 1610.- 2/Solar Convection and Differential Rotation.- Theory of Convection in a Deep Rotating Spherical Shell, and Its Application to the Sun.- The Pattern of Convection in the Sun.- On Theories of Solar Rotation.- Equilibrium Problem in a Rotating Convection Zone.- A Boussinesq Model for the Convection Zone and the Solar Angular Velocity.- Two-Dimensional Stochastic Motions and the Problem of Differential Rotation for Unrestricted Rotational Rates.- 3/Dynamo Theory and Magnetic Dissipation.- Mean-Field Magnetohydrodynamics of the Solar Convection Zone.- Mean-Field Magnetohydrodynamics as a Basis of Solar Dynamo Theory.- Dynamo in the Presence of Differential Rotation.- On Fast Magnetic Field Reconnection.- Dynamo Theory and the Solar Cycle.- Solar Magnetic Fields and Convection. VII: A Review of the Primordial Field Theory.- A Model of the Solar Cycle Driven by the Dynamo Action of the Global Convection in the Solar Convection Zone.- On the Distribution of Angular Velocity in the Sun.- On the Dipole-like Progressive Wave in the Photosphere.- 4/Stellar Activity of the Solar Type.- Stellar Activity of the Solar Type. Observational Aspects.- Chromospheric Variations in Main Sequence Stars.- The Internal Structure of the Sun and Solar Type Stars.- The Sun as a Magnetic Star.- Chromospheric Activity in F- and G-Stars.- Absolute Fluxes of K Chromospheric Emission on the H-R Diagram.- Double-Peaked Flare Events on Red Dwarf Stars and Solar 'Sympathetic' Flares.- Conclusions.- Summary of the Final Discussion on August 29.
