Basic Mechanisms of Solar Activity

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. Front Matter....Pages I-XVI Front Matter....Pages 1-1 The Enigma of Solar Activity....Pages 3-16 Front Matter....Pages 17-17 Differential Rotation and Global-Scale Velocity Fields....Pages 19-35 Differential Rotation and Giant Cell Circulation of the Solar Ca + -Network....Pages 37-40 Rotational Characteristics of Coronal Holes....Pages 41-43 On Differences in Differential Rotation....Pages 45-46 Large-Scale Solar Magnetic Fields....Pages 47-67 Small-Scale Solar Magnetic Fields....Pages 69-99 Investigation of Coronal Rotation by the Spectroscopic Method....Pages 101-106 Fast Variations of the Solar Rotation....Pages 107-111 About the Relation between the Limb Effect of the Redshift on the Sun and the Large-Scale Distribution of Solar Activity....Pages 113-118 Drift of Sunspots in Latitude....Pages 119-119 Velocities Observed in Supergranules....Pages 121-134 Long Term Evolution of Solar Sector Structure....Pages 135-135 Solar Cycle Evolution of the General Magnetic Field....Pages 137-143 Coronal Bright Points....Pages 145-146 Cyclical and Secular Variations of Solar Activity....Pages 147-190 Some Results of the Space Distribution of the Activation Vector of the Filaments in the 11-Year Cycle....Pages 191-197 Sequences of Large Sunspot Groups....Pages 199-202 Characteristic Features of Cyclic Change of Solar Activity after 1610....Pages 203-203 Front Matter....Pages 205-205 Theory of Convection in a Deep Rotating Spherical Shell, and Its Application to the Sun....Pages 207-228 Front Matter....Pages 205-205 The Pattern of Convection in the Sun....Pages 229-242 On Theories of Solar Rotation....Pages 243-295 Equilibrium Problem in a Rotating Convection Zone....Pages 297-297 A Boussinesq Model for the Convection Zone and the Solar Angular Velocity....Pages 299-300 Two-Dimensional Stochastic Motions and the Problem of Differential Rotation for Unrestricted Rotational Rates....Pages 301-302 Front Matter....Pages 303-303 Mean-Field Magnetohydrodynamics of the Solar Convection Zone....Pages 305-321 Mean-Field Magnetohydrodynamics as a Basis of Solar Dynamo Theory....Pages 323-344 Dynamo in the Presence of Differential Rotation....Pages 345-351 On Fast Magnetic Field Reconnection....Pages 353-366 Dynamo Theory and the Solar Cycle....Pages 367-388 Solar Magnetic Fields and Convection....Pages 389-407 A Model of the Solar Cycle Driven by the Dynamo Action of the Global Convection in the Solar Convection Zone....Pages 409-413 On the Distribution of Angular Velocity in the Sun....Pages 415-415 On the Dipole-Like Progressive Wave in the Photosphere....Pages 417-417 Front Matter....Pages 419-419 Stellar Activity of the Solar Type Observational Aspects....Pages 421-446 Chromospheric Variations in Main Sequence Stars....Pages 447-452 The Internal Structure of the Sun and Solar Type Stars....Pages 453-466 The Sun as a Magnetic Star....Pages 467-467 Chromospheric Activity in F- and G-Stars....Pages 469-471 Absolute Fluxes of K Chromospheric Emission on the H-R Diagram....Pages 473-473 Front Matter....Pages 419-419 Double-Peaked Flare Events on Red Dwarf Stars and Solar ‘Sympathetic’ Flares....Pages 475-475 Front Matter....Pages 477-477 Summary of the Final Discussion on August 29....Pages 479-481 Proceedings of IAU Symposium No. 71, held in Prague, Czechoslovakia, August 25-29, 1975