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Solar Astrophysics, 2nd, Revised Edition

Solar Astrophysics, 2nd, Revised Edition

Peter V. Foukal

ISBN: 978-3-527-61808-8 September 2008 480 Pages




This revised edition of Solar Astrophysics describes our current understanding of the sun - from its deepest interior, via the layers of the directly observable atmosphere to the solar wind, right out to its farthest extension into interstellar space. It includes a comprehensive account of the history of solar astrophysics, along with an overview of the key instruments throughout the various periods. In contrast to other books on this topic, the choice of material deals evenhandedly with the entire scope of important topics covered in solar research. The authors make the advances in our understanding of the sun accessible to students and non-specialists by way of careful use of relatively simple physical concepts. The book offers an incisive, reliable, and well-planned look at all that is fascinating and new in studies of the sun.

1 Development of the Ideas and Instruments of Modern Solar Research.

1.1 Early Telescopic Discoveries on the Sun.

1.2 The Spectroscope and Photography.

1.3 Solar-Terrestial Research and the New Astronomy.

1.4 Solar Chemical Composition and Energy Generation.

1.5 The Mt. Wilson Era of Large Telescopes.

1.6 Advances in Coronal Physics and in the Theory of Solar Activity.

1.7 Observations at Radio, Ultraviolet, and X-Ray Wavelengths.

1.8 The Solar Wind and Heliosphere.

1.9 Future Directions in Solar Instrumentation.

2 Radiative Transfer in the Sun's Atmosphere.

2.1 Photometric Principles.

2.1.1 The Radiative Intensity.

2.1.2 The Net Outward Flux and the Solar Constant.

2.2 The Radiative Transfer Equation.

2.2.1 The Optical Depth and Source Function.

2.2.2 Solution for Constant Source Function.

2.2.3 Solution for a Linear Source Function: The Eddington-Barbier Relation.

2.3 Thermodynamic Equilibrium.

2.3.1 The Planck Function.

2.3.2 Kirchhoff's Law.

2.3.3 Local Thermodynamic Equilibrium (LTE).

2.3.4 The Brightness- and Effective Temperatures.

2.4 The Gray Atmosphere.

2.4.1 Formulation of the Problem.

2.4.2 Gray Limb Darkening in the Eddington Approximation.

2.4.3 The Photospheric Level Identified with Radiation at Teff.

2.4.4 Radiative Diffusion.

2.5 Radiative Transfer in the Fraumhofer Lines.

2.5.1 Formation of Fraunhofer Lines.

2.5.2 The Transfer Equation for Lines.

2.5.3 The Milne-Eddington Model.

2.5.4 Comparison with Observations of Line Depth near Disk Center.

2.5.5 Comparison with Observed Center-to-Limb Behavior.

3 Solar Spectroscopy.

3.1 A Survey of the Sun's Spectrum.

3.2 Atomic Structure.

3.3 Space Quantization and the Zeeman and Stark Effects.

3.3.1 The Zeeman Effect.

3.3.2 The Stark Effect.

3.4 Multiplet Rules for Transitions.

3.5 Atomic Transitions and their Excitation.

3.6 Rates for Radiative Transitions.

3.7 Boltzmann Equilibrium and the Saha Equation.

3.8 Rate Equations in Statistical Equilibrium.

3.9 Line Broadening.

3.9.1 Thermal and Turbulent Doppler Broadening.

3.9.2 Radiation Damping and Pressure Broadening.

3.9.3 Broadening by Self-Absorption.

3.9.4 Analysis of the Observed Profile of a Spectral Line.

3.10 Molecules on the Sun.

4 Dynamics of Solar Plasmas.

4.1 Hydrostatic Equilibrium.

4.1.1 Equilibrium in a Homogeneous Gravitational Field.

4.1.2 Self-Gravitating Atmospheres.

4.1.3 The Polytropic Approximation.

4.2 The Equations of Motion.

4.2.1 Euler's Equation.

4.2.2 Viscous Forces and the Navier-Stokes Equation.

4.2.3 The Equation of Continuity.

4.2.4 The Heat-Balance Equation.

4.2.5 Conservation of Total Energy.

4.3 The Influence of Magnetic Fields in Solar Plasma Dynamics.

4.3.1 The Lorentz Force.

4.3.2 The Importance of Self-induction.

4.3.3 The Diffusive and "Frozen-in" Approximations.

4.4 Wave Motions in the Sun.

4.4.1 Types of Waves Expected and Observed.

4.4.2 Sound Waves.

4.4.3 Simple Waves and Shock Formation.

4.4.4 Properties of Shock Waves.

4.4.5 Magnetohydrodynamic Waves.

4.4.6 Internal Gravity Waves.

4.4.7 Plasma Oscillations.

4.5 Charged Particle Dynamics.

4.5.1 Validity of the Continuum Approximation and of Thermal Equilibrium.

4.5.2 Charged Particle Motions.

5 The Photosphere.

5.1 Observations of the Quiet Photosphere.

5.1.1 Limb Darkening.

5.1.2 Observed Properties of Granulation.

5.1.3 The Supergranulation and Photospheric Network.

5.2 Construction of a Photospheric Model.

5.2.1 Physical Assumptions.

5.2.2 Determination of the Temperature Profile from Continuum Limb Darkening.

5.3 Determination of the Photospheric Opacity.

5.3.1 The Empirical Technique.

5.3.2 The Sources of Photospheric Opacity.

5.4 Physical Structure and Energy Balance of the Photosphere.

5.4.1 Models of Photospheric Structure.

5.4.2 Comparison with Observations.

5.4.3 Energy Transport Mechanisms in the Photosphere.

5.5 The Photospheric Chemical Composition and the Curve of Growth.

5.5.1 The Theoretical Curve of Growth.

5.5.2 Comparison with the Empirical Curve.

5.6 The Sun's Chemical Composition.

6 The Sun's Internal Structure and Energy Generation.

6.1 Equations of Stellar Structure.

6.1.1 Mechanical Equilibrium.

6.1.2 Energy Transport.

6.1.3 Boundary Conditions.

6.2 Physical Parameters Required for the Solution.

6.2.1 Chemical Composition.

6.2.2 The Mean Molecular Weight.

6.2.3 The Ratio of Specific Heats.

6.2.4 The Radiative Opacity.

6.2.5 Energy Generation Processes.

6.3 Nuclear Reactions in the Sun's Interior.

6.3.1 Factors That Determine the Dominant Reactions.

6.3.2 The Proton-Proton Chain.

6.3.3 The Carbon-Nitrogen Cycle.

6.3.4 Nuclear Energy Generation Rates.

6.4 The Standard Model of Physical Conditions in the Solar Interior.

6.5 Observational Tests of the Standard Model.

6.5.1 Solar Neutrino Observations.

6.5.2 Lithium and Beryllium Abundances.

6.5.3 Stellar Structure and Evolution.

6.5.4 Geological and Climatological Evidence.

6.5.5 The Sun's Angular Momentum and Shape.

6.5.6 Solar Oscillations.

7 Rotation, Convection, and Oscillations in the Sun.

7.1 Observations of Solar Rotation.

7.1.1 Photospheric Doppler Measurements.

7.1.2 Helioseismic Measurements of Rotation in the Solar Interior.

7.1.3 Tracer Measurements.

7.2 Measurements on Convection.

7.2.1 Observations of Convection at the Photosphere.

7.2.2 Comparison with Laboratory Measurements.

7.3 Dynamics of Solar Convection and Rotation.

7.3.1 Condition for Onset of Convection.

7.3.2 Gravity Waves.

7.3.3 Mixing Length Theory.

7.3.4 Dynamics of Convection in a Plane Layer.

7.3.5 Models of Granulation.

7.3.6 Dynamics of Supergranulation.

7.3.7 Dynamics of the Solar Interior.

7.4 Observations of Solar Oscillations.

7.4.1 The 5-min Oscillations.

7.4.2 Oscillations of Longer and Shorter Periods.

7.5 Interpretation of Solar Oscillations.

7.5.1 Resonances in the Sun.

7.5.2 Oscillation Modes of the Solar Interior.

7.5.3 Excitation and Damping Mechanisms.

7.5.4 Comparison of the Observed and Calculated Properties of the p-Modes.

7.5.5 Oscillations as a Probe of the Solar Interior.

8 Observations of Photospheric Activity and Magnetism.

8.1 Sunspot Observations.

8.1.1 Structure of the Umbra and Penumbra.

8.1.2 Birth and Evolution of Spot Groups.

8.1.3 Photometry and Spectra of Umbrae.

8.1.4 Mass Motions and Oscillations.

8.2 Dynamics of Spots.

8.2.1 Thermal Structure of the Umbra.

8.2.2 Why Spots Are Cool.

8.2.3 Why Spots Cause Dips in the Solar Luminosity.

8.2.4 Dynamics of Sunspot Evolution.

8.3 Faculae.

8.3.1 Structure and Evolution.

8.3.2 Physical Measurements.

8.3.3 Why Faculae Are Bright.

8.4 Observations of Solar Magnetism.

8.4.1 The Sunspot Magnetic Field.

8.4.2 Photospheric Fields in Faculae and Magnetic Network.

8.4.3 Large-Scale Structure and Evolution of the Photospheric Field.

8.4.4 Global Structure of the Sun's Magnetic Field.

9 The Chromosphere and Corona.

9.1 The Chromosphere.

9.1.1 Observations of Structures and Motions at the Limb.

9.1.2 Observations on the Disk.

9.1.3 Physical Conditions.

9.1.4 Energy Balance.

9.1.5 Chromospheric Heating.

9.1.6 Dynamics of Spicules and Fibrils.

9.2 The Corona and Transition Region.

9.2.1 Spectrum and Radiation Mechanisms.

9.2.2 Structures of the Corona and Transition Region.

9.2.3 Magnetic Fields and Plasma Motions.

9.2.4 Physical Conditions in Closed and Open Magnetic Structures.

9.2.5 Heating and Dynamics of Coronal Loops and Holes.

10 Prominences and Flares.

10.1 Prominences and Filaments.

10.1.1 Observations and Physical Conditions.

10.1.2 Dynamics.

10.2 Flares.

10.2.1 Observations and Physical Conditions.

10.2.2 Energy Release and Dynamics.

10.2.3 Acceleration of Energetic Charged Particles.

11 Dynamics of the Solar Magnetic Field.

11.1 Dynamics of Solar Magnetic Flux Tubes.

11.1.1 Dynamical Equilibrium and Geometry.

11.1.2 Dynamical Stability.

11.1.3 Thermal Instability.

11.1.4 Steady Flows.

11.1.5 Oscillations and Waves.

11.1.6 Magnetic Field Dissipation.

11.2 Activity Behavior over the Solar Cycle.

11.2.1 The Sunspot Number and Other Activity Indices.

11.2.2 Time Behavior of the Sun's Magnetic Field.

1.1.2 Long-Term Behavior of Solar Activity.

11.3 Dynamics of the Solar Magnetic Cycle.

11.3.1 The Babcock Model of the Solar Cycle.

11.3.2 Dynamical Dynamo Models.

12 The Solar Wind and Heliosphere.

12.1 Structure of the Solar Wind.

12.1.1 In Situ Measurements of Particles and Fields.

12.1.2 Observations Out of the Ecliptic Plane.

12.1.3 Cosmic Rays.

12.1.4 Interplanetary Gas and Dust.

12.1.5 Structure of the Heliosphere.

12.2 Transient Features in the Solar Wind.

12.2.1 High-Speed Streams.

12.2.2 Interplanetary Shock Waves.

12.2.3 Coronal Mass Ejections (CME's).

12.3 Dynamics of the Solar Wind.

12.3.1 Thermal Conductivity of the Corona.

12.3.2 Expansion of the Corona.

12.3.3 Geometry of the Interplanetary Magnetic Field.

12.3.4 Energy and Angular Momentum Fluxes.

12.3.5 Sources of the Wind.

13 The Sun, Our Variable Star.

13.1 The Sun Compared to other Stars.

13.1.1 The Sun's Location and Proper Motion in the Galaxy.

13.1.2 Mass, Chemical Composition and Spectrum.

13.1.3 Luminosity, Radius, and Effective Temperature.

13.1.4 Chromospheric and Coronal Radiations.

13.1.5 Stellar Winds and Mass Loss.

13.1.6 Angular Momentum and Magnetism.

13.2 Evolution of the Sun.

13.2.1 The H-R Diagram and Stellar Evolution.

13.2.2 The Sun's Future Evolution.

13.2.3 The Early Sun.

13.3 Solar and Stellar Variability.

13.3.1 Observations of Stellar Activity.

13.3.2 Mechanisms of Stellar Activity.

13.3.3 The Sun's Variable Outputs.

13.3.4 Prediction of Solar Activity and Space Weather.