Solar photosphere : structure, convection, and magnetic fields : proceedings of the 138th Symposium of the International Astronomical Union, held in Kiev, U.S.S.R., May 15-20, 1989

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. Front Matter....Pages i-xii Front Matter....Pages 1-1 Models of the Solar Photosphere....Pages 3-22 Thermal Bifurcation Of the Outer Photosphere....Pages 23-27 Temperature Diagnostics of the Upper Photosphere....Pages 29-34 Solar Oscillator Strengths As A Diagnostic Tool....Pages 35-40 Average Variations Of Photospheric FeI and FeII Line Parameters As Function Of The Magnetic Filling Factor....Pages 41-46 Front Matter....Pages 47-47 High Resolution Observations of the Photosphere....Pages 49-66 Properties Of The Solar Granulation....Pages 67-79 Analysis of the Solar Granulation in the Opacity Minimum Region....Pages 81-84 Fine Structure of Photospheric Faculae....Pages 85-96 Bright Features In The Intergranular Region....Pages 97-100 Front Matter....Pages 101-101 Empirical Models Of Photospheric Flux Tubes....Pages 103-120 Empirical Photospheric Fluxtube Models From Inversion of Stokes V Data....Pages 121-124 Properties of Photospheric Fluxtubes Derived From Magnetograph Observations....Pages 125-128 Small-Scale Magnetic Features Observed in the Photosphere....Pages 129-146 High-Resolution Observations of Emerging Magnetic Fields and Flux Tubes in Active Region Photosphere....Pages 147-152 Small Scale Motions Over Concentrated Magnetic Field Regions of the Quiet Sun....Pages 153-156 Small Scale Magnetic Structures in Active Centers....Pages 157-160 Theoretical Aspects Of Small-Scale Photospheric Magnetic Fields....Pages 161-179 Model Calculations of the Photospheric Layers of Solar Magnetic Fluxtubes....Pages 181-184 Wave Heating In Magnetic Flux Tubes....Pages 185-188 Front Matter....Pages 189-189 Solar Magnetoconvection....Pages 191-211 Results from 2-D Numerical Simulations of Solar Granules....Pages 213-216 Waves and Oscillations in the Non-Magnetic Photosphere....Pages 217-228 Waves and Oscillations in Magnetic Fluxtubes....Pages 229-249 On the 5-Minute Photospheric Oscillation and its Modeling....Pages 251-254 Classification of Magnetoatmospheric Modes in Sunspot Umbrae....Pages 255-258 The Observational Signature of Flux Tube Waves and an Upper Limit on the Energy Flux Transported by them....Pages 259-262 Magnetic Flux Concentration by Siphon Flows in Isolated Magnetic Flux Tubes....Pages 263-266 Electric Currents in the Atmosphere of the Sun....Pages 267-271 Generation Of Magnetic Fields And Electric Currents In The Solar Photosphere....Pages 273-277 Front Matter....Pages 279-279 Global Evolution of Photospheric Magnetic Fields....Pages 281-295 Origin of the Sun’s Differential Rotation....Pages 297-307 The Sun’s Rotation Rate as Inferred from Magnetic Field Data....Pages 309-314 Generators of Solar Differential Rotation and Implications of Helioseismology....Pages 315-320 Asymmetry Of Merging Flux Loops Caused By Radial Differential Rotation....Pages 321-324 Convection And Its Stability In The Equatorial Regions Of The Convection Zone....Pages 325-328 Inverse Cascade in Hydrodynamic Turbulence and its Role in Solar Granulation....Pages 329-332 Generation of Torsional Oscillations in the Sun....Pages 333-340 Front Matter....Pages 341-341 Order and Chaos in the Solar Cycle....Pages 343-353 Symmetry Breaking in the Solar Dynamo: Nonlinear Solutions....Pages 355-358 Front Matter....Pages 341-341 Excitation of Dynamo Modes....Pages 359-374 Study of Sun’s ‘Hydromagnetic’ Oscillations Using Sunspot Data....Pages 375-378 Variation of Even and Odd Parity in the Solar Dynamo....Pages 379-382 Self-Ordering of Photospheric Magnetic Fields....Pages 383-386 Torsional Oscillations and the Solar Dynamo Regime....Pages 387-390 Large-Scale Internal Magnetic Field of the Sun....Pages 391-394 Front Matter....Pages 395-395 Observing, Modeling, And Understanding Stellar Granulation....Pages 397-415 A Model For Stellar Convection and Spectral Line Asymmetries....Pages 417-420 Comparative Analysis of Physical Conditions in the Solar and Procyon Atmospheres....Pages 421-425 Magnetic Fields on Solar-Like Stars: The First Decade....Pages 427-441 Results Of Coordinated Multiwavelength Observations Of Solar-Type Stars....Pages 443-446 Nonlinear Dynamo Modes and Timescales of Stellar Activity....Pages 447-453 Does a Common Dynamo Mechanism Exist for Lower Main Sequence Stars ?....Pages 455-459 Front Matter....Pages 461-461 Ground Based and Space Future Prospects in Solar Interferometry Applied to the Photosphere....Pages 463-467 New Observational Aspects....Pages 469-487 Outstanding Theoretical Problems....Pages 489-499 Summary Lecture....Pages 501-516 Back Matter....Pages 517-560 Proceedings of the 138th Symposium of the International Astronomical Union, held in Kiev, U.S.S.R., May 15-20, 1989