The Sun As a Variable Star: Solar and Stellar Irradiance Variations : Proceedings of the 143rd Colloquium of the International Astronomical Union Held in the Clarion Harvest House, Boulder, Colorado, June 20–25, 1993

The IAU Colloquium No. 143 "The Sun as a Variable Star: Solar and Stellar Irradiance Variations" was held on June 20 - 25, 1993 at the Clarion Harvest House, Boulder, Colorado, USA. The main objective of this Colloquium was to review the most recent results on the observations, theoretical interpreta­ tions, and empirical and physical models of the variations observed in solar and stellar irradiances. A special emphasis of the Colloquium was to discuss the results gained on the climatic impact of solar irradiance variability. The study of changes in solar and stellar irradiances has been of high interest for a long time. Determining the absolute value of the luminosity of stars with different ages is a crucial question for the theory of stellar evolu­ tion and energy production of stellar interiors. Observations of the temporal changes of solar and stellar irradiances - in the entire spectral band and at different wavelengths - provide an additional tool for studying the physical processes below the photosphere and in the solar- stellar atmospheres. Since the Sun's radiative output is the main driver of the physical processes with­ in the Earth's atmosphere, the study of irradiance changes is an extremely important issue for climatic studies as well. Climatic models show that small, but persistent changes in solar irradiance may influence the Earth's climate. Front Matter....Pages i-xii Cryogenic Solar Absolute Radiometer — CSAR....Pages 1-8 A Review of the Nimbus-7 ERB Solar Dataset....Pages 9-12 Long-Term Variations in Total Solar Irradiance....Pages 13-21 Solar Total Irradiance Variability from Sova 2 on Board Eureca....Pages 23-29 The Periodicity of Solar Activity Cycles....Pages 31-34 Maximum and Minimum Temperatures at Armagh Observatory, 1844–1992, and the Length of the Sunspot Cycle....Pages 35-42 Photometer “Difos” for the Study of Solar Brightness Variations....Pages 43-46 The Brightness of the Solar Disk in the Continuum in the Region 1.0–2.4 μM....Pages 47-52 Irradiance Observations of the 1–8 Å Solar Soft X-Ray Flux from Goes....Pages 53-59 Comparisons of the MG II Index Products from the NOAA-9 and NOAA-11 SBUV/2 Instruments....Pages 61-68 The Solar Ca II K Index and the Mg II Core-To-Wing Ratio....Pages 69-76 Solar EUV Flux Variations Near Activity Maxima....Pages 77-80 The Xray-Euv Spectrum of Optically Thin Plasmas....Pages 81-86 List of Stars Recommended as Spectrophotometric Standards....Pages 87-90 Variable Stars with the Hipparcos Satellite....Pages 91-96 Variation of the Solar Diameter from Solar Eclipse Observations, 1715–1991....Pages 97-104 Latitudinal Variation of the Solar Limb-Darkening Function....Pages 105-110 Improvement of the Photometric Sunspot Index and Changes of the Disk-Integrated Sunspot Contrast with Time....Pages 111-118 Modelling Solar Irradiance Variations with an Area Dependent Photometric Sunspot Index....Pages 119-124 On the Cause of Total Irradiance Variations Observed by the CCD Solar Surface Photometer....Pages 125-130 Latitude and Cycle Variations of the Photospheric Network....Pages 131-137 Variability of the Solar Chromospheric Network Over the Solar Cycle....Pages 139-144 A Yohkoh Search for “Black-Light Flares”....Pages 145-151 Coronal Index of Solar Activity: Years 1939–1963....Pages 153-159 Rotational Characteristics of the Green Solar Corona: 1964-1989....Pages 161-166 Solar Cycle Variation of the Microwave Spectrum and Total Irradiance....Pages 167-173 Solar Brightness Distribution and its Variability at 3 Millimeter Wavelength....Pages 175-180 Latitudinal Variability of Large-Scale Coronal Temperature and its Association with the Density and the Global Magnetic Field....Pages 181-188 Active Region Evolution and Solar Flux Variations....Pages 189-194 On the Variability of Some Characteristics of Solar Radiative Flux....Pages 195-200 Lyman-Alpha Line Intensity as a Solar Activity Index in the Far Ultraviolet Range....Pages 201-206 Modeled Soft X-Ray Solar Irradiances....Pages 207-215 Cosmic Rays as an Indicator of Solar Activity....Pages 217-219 Meridional Motions of Sunspot Groups during Eleven Activity Cycles....Pages 221-226 Radiation-Hydrodynamic Waves and Global Solar Oscillations....Pages 227-239 Excitation of Solar Gravity Waves....Pages 241-246 Solar Noise Simulations in Irradiance....Pages 247-252 Secular Variations in the Spectrum of Solar P-Modes....Pages 253-260 Solar Cycle Variations in P-modes and Chromospheric Magnetism....Pages 261-266 Sunspot Numbers Uncertainties and Parametric Representations of Solar Activity Variations....Pages 267-274 “Star as a Sun” Observations in Seismology of Distant Stars....Pages 275-282 Rotating Convection and the Solar Differential Rotation....Pages 283-290 Variations of the Magnetic Fields of the Sun and the Earth In 7–50 Day Periods....Pages 291-296 Distinction between the Climatic Effects of the Solar Corpuscular and Electromagnetic Radiation....Pages 297-302 EUDOSSO: A Space Project for Solar Oscillations and Long Term Variability Relevant to Climatic Changes....Pages 303-308 Solar Magnetic and Bolometric Cycles Recorded in Sea Sediments....Pages 309-312 Long-Term Persistence of Solar Activity....Pages 313-313 Stellar Irradiance Variations Due to Surface Temperature Inhomogeneities....Pages 314-314 Voyager EUV Solar Spectra During 1981–1993....Pages 315-315 On P-Mode Oscillations in Stars from 1 M⊙ to 2 M⊙....Pages 316-316 Facular Excess Radiation and the Energy Balance of Solar Active Regions....Pages 317-317 The 73-Day Periodicity of the Flare Index during the Current Solar Cycle 22....Pages 318-318 Phase differences between irradiance and velocity low degree solar acoustic modes revisited....Pages 319-319 The papers in this volume represent the most up to date research contributions on the observations, theoretical interpretations, and empirical and physical models of variations observed in solar and stellar irradiances, as well as on Sun--climate connections. Both theoretical studies and irradiance observations show that the energy output of the Sun and solar-type stars varies, changing on time scales related to the short-term surface manifestations of solar/stellar magnetic activity as well as long-term modulations driven by processes in the interiors of the stars. Papers presented in this book point out that at the Earth these variations influence the terrestrial climate, radiative environment, and upper atmospheric chemistry.