The Sun And Cool Stars: Activity, Magnetism, Dynamos: Proceedings Of Colloquium No. 130 Of The International Astronomical Union Held In Helsinki, Finland, 17-20 July 1990 (lecture Notes In Physics)

The contributions in this volume report recent studies on the sun and late-type stars. Particular emphasis is placed on observations that are relevant to the question of large-scale magnetic activity, and also on the theoretical (dynamo) models for such activity. Experimental papers deal with surface imaging techniques. Explicit computer simulations of hydromagnetic turbulence give insight into the magnetic topology and associated fluid motions, especially near the base of the convection zone. In addition, mean-field dynamo models are presented. The book addresses researchers but should also Äjbe useful for graduate students. The confrontation of mean-field theories with numerical simulations....Pages 1-14 On numerical studies of solar/stellar convection....Pages 15-26 Turbulent Convection: A New Model....Pages 27-32 Large scale convection in stars : Towards a model for the action of coherent structures....Pages 33-36 Magnetoconvection patterns in rotating convection zones....Pages 37-56 Stellar convection as a low Prandtl number flow....Pages 57-61 Convective overshoot as a source of helicity....Pages 62-66 Topological pumping in the lower overshoot layer....Pages 67-70 Diffusion of particles, heat and magnetic fields in compressible turbulent media....Pages 71-74 The spatial structure of homogeneous turbulence at high Reynolds number....Pages 75-79 Compressible MHD in spherical geometry....Pages 80-85 The role of overshoot in solar activity: A direct simulation of the dynamo....Pages 86-88 Vector potential magnetic null points....Pages 89-91 Magnetic tubes in overshooting compressible convection....Pages 92-94 Convective cores in stellar models....Pages 95-97 Rotational effects on Reynolds stresses in the solar convection zone....Pages 98-100 Stable and unstable solutions of the nonlinear dynamo problem....Pages 101-111 Nonlinear nonaxisymmetric dynamos for active stars....Pages 112-116 Waves of Solar Activity....Pages 117-128 Non-steady global magnetic fields in kinematic theory....Pages 129-134 Asymptotic methods in the nonlinear mean-field dynamo....Pages 135-139 Fractal flux tubes of the solar magnetic field....Pages 140-146 αΛ -dynamos....Pages 147-150 Fossil magnetic fields and activity of young stars....Pages 151-153 The sun's internal differential rotation from helioseismology....Pages 155-171 Λ -effect, meridional flow and the differential solar rotation....Pages 172-177 Differential rotation as an axisymmetric resonant mode of convection....Pages 178-181 The solar internal rotation and its implications....Pages 182-186 The toroidal magnetic field inside the Sun....Pages 187-189 The transfer of large-scale magnetic field by radial inhomogeneity of the material density in the rotating convection zone....Pages 190-192 Diagnostics of the solar dynamo using the observed pattern of surface magnetic fields....Pages 193-212 The large-scale magnetic field in the global solar cycle: observational aspects....Pages 213-217 Evolution of large and small scale magnetic fields in the sun....Pages 218-222 The solar dynamo....Pages 223-233 A topological model of the solar magnetic field reversals....Pages 234-236 Solar internal rotation, the boundary layer dynamo and latitude distribution of activity belts....Pages 237-240 Solar rotation over solar cycle 21....Pages 241-245 Sun-as-a-star: Its convective signature and the activity cycle....Pages 246-251 The hel ⋋10830 Å line as an indicator of the chromospheric and coronal activity of the sun....Pages 252-265 The rotational modulation of ca II K in the sun....Pages 266-267 The prolonged minima and maxima of solar activity....Pages 268-270 The longer term evolution of magnetic field and mass flow in a decaying active region....Pages 271-274 The main component analysis of the longitudinal distribution of solar activity....Pages 275-276 Fe I line asymmetries and shifts caused by pressure broadening....Pages 277-278 Rotation of large scale patterns on the solar surface as determined from filament and millimeter data....Pages 279-281 Large scale patterns on the solar surface indicated by microwave observations....Pages 282-284 The solar corona over the recent saros....Pages 285-287 The history of activity of the Sun and its rotational period on the ZAMS....Pages 288-293 The differential rotation and evolution of spots on UX Arietis from a sequence of Doppler images....Pages 295-308 The art of surface imaging....Pages 309-320 Surface imaging of El Eri....Pages 321-325 Towards magnetic images of rapidly rotating late-type stars....Pages 326-329 Chromospheric surface structures on El Eridani and HD 199178....Pages 330-332 Activity, colour anomalies and temperature determination in solar-type stars....Pages 333-335 Dynamo action in evolved stars....Pages 336-341 The boundary between the magnetic fields of ap stars and the fields of solar-type stars....Pages 342-346 Doppler mapping of CP-star surfaces with weak and strong magnetic fields....Pages 347-349 Temperature variations on the surface of the Si-star CU Virginis....Pages 350-352 Learning about stellar dynamos from long-term photometry of starspots....Pages 353-369 Starspot activity on short-period RS CVn stars....Pages 370-372 Variations in spottedness of photosphere and chromosphere of the flare star EV Lac....Pages 373-375 Surface inhomogeneities on the W UMa star AC Bootis....Pages 376-377 Long-term starspot behavior of BY Dra and EV Lac....Pages 378-380 The spot activity of FK Comae Berenices....Pages 381-383 On the existence of solar-type activity in the secondary components of cataclysmic variables....Pages 384-385 Radial velocity variability of K giants....Pages 386-388 Recent advances in the observation and analysis of stellar magnetic fields....Pages 389-400 Limits on the magnetic flux of a pre-main sequence star....Pages 401-406 Stellar zeeman analyses: Effects of multi-component atmospheres....Pages 407-410 Multi-line Zeeman analysis....Pages 411-413 A new technique to measure magnetic field strength in active stars....Pages 414-416 Magnetic flux determination in late-type dwarfs....Pages 417-419 Linear polarization and magnetic fields in cool stars....Pages 420-423 Long-term polarimetric activity of the cool supergiant μ Cephei....Pages 424-426 Polarimetric observations of active cool binaries....Pages 427-429 Magnetic fields and filling factors in late-type stars: Predictions from dynamo theory....Pages 430-434 Activity of relatively close binaries....Pages 435-439 Two kinds of activity in late-type stars....Pages 440-442 Ca II H and K and H α , and Li abundances in the pleiades late K main-sequence....Pages 443-445 Is ξ Boo AB a young or an evolved system? a model atmosphere analysis....Pages 446-448 Spectroscopic analysis of HR 1099....Pages 449-451 Recent advances in our understanding of chromospheric and coronal heating mechanisms....Pages 452-462 Ca II H high-resolution spectral monitoring of active late-type dwarfs....Pages 463-465 The onset of chromospheres in A-type stars: The altair affair....Pages 466-470 Hα and NaD line variability in RY Tauri....Pages 471-476 He I 5876 å line in the study of chromospheric activity in F-type MS stars....Pages 477-479 The age evolution of Ca II emission in late type stars....Pages 480-482 Ca II H and K spectroscopy of ER Vul....Pages 483-485 The variations of the Hα line of HD199178....Pages 486-488 Hα emission in the giant components of RS CVn systems....Pages 489-491 Spectroscopy of southern active stars....Pages 492-493 Full phase coverage of by Dra with the VLA....Pages 494-497 Coronal magnetic fields of Algol binaries from microwave spectra....Pages 498-500 On the coronal activity of RS CVn systems....Pages 501-503 Flare rate spectra as a possibility of diagnostics of convection zones in stars....Pages 504-506 Observations relating to stellar activity, magnetism and dynamos....Pages 507-514 Concluding summary: Theoretical aspects....Pages 515-521 This volume reports recent studies on the sun and late-type stars, emphasizing observations that are relevant to the question of large-scale magnetic activity and the theoretical (dynamo) models for such activity. Experimental papers deal with surface imaging techniques.