The Many Faces of the Sun, Softcover reprint of the original 1st ed. 1999
A Summary of the Results from NASA’s Solar Maximum Mission

A decade of observations of the Sun with NASAs Solar Maximum Mission satellite has led to important discoveries in solar and atomic physics. This book presents the first comprehensive review of these results in a single volume, providing a snapshot of the current state of knowledge of solar physics. Chapters provide insight into the structure, composition and activity of the Sun, with coverage of topics such as solar flares, variations in the solar irradiance, coronal mass ejections, and spectroscopy.

1. The Solar Maximum Mission.- 1.1 The Origins of the Mission.- 1.2 Scientific Objectives of the Mission.- 1.3 The SMM Instrument Package.- 1.3.1 The ?-Ray Spectrometer (GRS).- 1.3.2 The Hard X-Ray Burst Spectrometer (HXRBS).- 1.3.3 The Hard X-Ray Imaging Spectrometer (HXIS).- 1.3.4 The Bent Crystal Spectrometer (BCS).- 1.3.5 The Flat Crystal Spectrometer (FCS).- 1.3.6 The Ultraviolet Spectrometer/Polarimeter (UVSP).- 1.3.7 The Coronagraph/Polarimeter (C/P).- 1.3.8 The Active Cavity Radiometer Irradiance Monitor (ACRIM).- 1.4 Scientific Discoveries.- 1.5 Concluding Remarks.- 2. Solar Irradiance Variations.- 2.1 Development of Solar Irradiance Monitors.- 2.1.1 Early Space-Based Solar Observations.- 2.1.2 Sounding-Rocket Experiments.- 2.1.3 Nimbus-7 ERB Experiment.- 2.1.4 The SMM ACRIM Experiment.- 2.1.5 ACRIM I Results During Solar Cycles 21 and 22.- 2.1.5.1 Variability on Solar Cycle Timescales.- 2.1.6 Level of Significance of the Long-Term Data Base.- 2.1.7 Variability on Solar Active-Region Timescales.- 2.1.7.1 The “Sunspot Deficit” Effect.- 2.1.7.2 Facular “Excess” Effect.- 2.1.7.3 Energy Balance in Active Regions.- 2.1.8 Short-Term Variability: Global Oscillations.- 2.2 Models of the Solar-Cycle TSI Variation.- 2.2.1 Active-Region Timescales.- 2.2.2 Solar-Cycle Timescales.- 2.2.3 Shortcomings of Linear Regression Models.- 2.2.4 Multivariate Spectral Analysis.- 2.3 ACRIM I and Succeeding Observations.- 2.3.1 Solar Monitoring by ERBE Experiments.- 2.3.2 ACRIM II on UARS.- 2.3.3 Measurement Strategy for the Climate TSI Data Base.- 2.4 The Long-Term Climate TSI Data Base.- 2.4.1 ACRIM II Relationship to ACRIM I, ERB and ERBS.- 2.4.2 Sustaining the TSI Database.- 2.4.3 Future Total Solar Irradiance Monitoring.- 3. Active Regions.- 3.1 Magnetic Field Strength and Structure.- 3.1.1 Results Prior to SMM.- 3.1.2 First Results with SMM.- 3.1.3 Subsequent Results: 1983–1987.- 3.1.4 The Coronal Magnetic Structures Observing Campaign.- 3.1.5 Coronal Magnetic Field Studies after SMM.- 3.2 Dynamics and Heating of the Solar Corona.- 3.2.1 FCS Line-Broadening Measurements.- 3.2.1.1 Large Nonthermal Velocities.- 3.2.1.2 Spatial Variations.- 3.2.1.3 Correlation Studies.- 3.2.2 FCS Line-Broadening Data.- 3.2.3 Interpreting the FCS Line Broadening.- 3.2.3.1 Constraints on Mass Motions.- 3.2.3.2 Link to Heating.- 3.2.3.3 Discussion.- 3.2.4 Coronal Heating, Magnetic Fields, and Flares.- 3.2.4.1 UVSP Observations of Active Regions.- 3.3 Transition Region Brightenings: UV Microflares.- 3.4 Sunspots.- 3.4.1 Magnetic Field and Height of the Transition Region.- 3.4.2 Sunspot Plumes.- 3.4.3 Sunspot Flows.- 3.4.3.1 Horizontal Flows.- 3.4.3.2 Vertical Flows.- 3.4.3.3 Nonthermal Line Broadening.- 3.4.3.4 Umbral Oscillations.- 3.4.3.5 A Look Backward, a Look Forward.- 3.5 Prominences and Filaments.- 3.5.1 Prominence Environment and Structure.- 3.5.2 Steady Flows in Prominence Material.- 3.5.3 Activity in Prominences.- 3.5.4 Postflare Loops and Surges.- 3.5.5 Conclusion.- 4. Coronal Abundances.- 4.1 Flare X-Ray Measurements from BCS.- 4.1.1 Calcium Abundance.- 4.1.2 Fe/H and Fe/Ca Abundance.- 4.1.3 Relative Abundances of Ar, Ca, and Fe in Flares.- 4.1.4 Factors Affecting Abundance Determinations from X-Ray Spectra.- 4.2 FCS Abundances.- 4.2.1 FCS Active-Region Abundances.- 4.2.1.1 Abundance Variability in Active Regions.- 4.2.1.2 Impact of Resonance Scattering.- 4.2.1.3 Assessment of FCS Active-Region Abundance Results.- 4.2.2 FCS Flare Abundance Studies.- 4.2.2.1 Coronal Cl/S and Ar/S Measurements.- 4.2.2.2 DEM Studies of Flare Abundances.- 4.3 Determination of Solar Abundances by Solar Flare ?-Ray Spectrometry.- 4.3.1 ?-Ray Spectral Analysis.- 4.3.2 ?-Ray Results.- 4.4 Solar Energetic Particles.- 4.4.1 Major Proton Events.- 4.4.2 CIR Events from Coronal Holes.- 4.4.3 Impulsive Flare Events.- 4.5 Theory of Abundance Fractionation.- 4.5.1 Gravitational Settling.- 4.5.2 Pressure Gradient and Stationary Diffusion.- 4.5.3 Ion-Neutral Separation Due to Currents.- 4.5.4 Ion-Neutral Separation Due to Electromagnetic Forces.- 4.5.5 Discussion.- 4.6 Summary.- 5. Coronal Mass Ejections.- 5.1 Nature and Structure of Coronal Mass Ejections.- 5.1.1 Specific Examples.- 5.1.2 Pre-Ejection “Swelling” of the Coronal Helmet Streamer.- 5.1.3 Formation and Outward Propagation of the Mass Ejection.- 5.1.4 Post-Ejection Depletion of the Helmet Streamer Region.- 5.1.5 Pre-Eruption Evolution of the Prominence and Corona.- 5.1.6 The Mass Ejection and Prominence Eruption.- 5.1.7 The Post-Ejection Corona.- 5.1.8 Summary.- 5.1.9 Some Measured Properties.- 5.1.9.1 Shape or Geometry.- 5.1.9.2 Angular Size.- 5.1.9.3 Locations.- 5.2 The Propagation of Mass Ejections Through the Corona.- 5.3 The Origin of Coronal Mass Ejections.- 5.3.1 Some Essential Facts.- 5.3.1.1 Large Spatial Scales.- 5.3.1.2 Occurrence in (and Disruption of) Closed Magnetic Structures, Including Those not Related to Active Regions.- 5.3.1.3 The Huge Variability in the Phenomenon.- 5.3.1.4 Mass Ejections and Prominence Eruptions.- 5.3.2 Mass Ejections and “Optical” Solar Flares.- 5.3.3 Mass Ejections and Soft X-Ray Flares.- 5.3.3.1 Formation (and Acceleration) of a Mass Ejection Within the SMM Field of View.- 5.3.3.2 Formation (and Initial Acceleration) of a Mass Ejection in the Low Corona.- 5.3.3.3 Association with an X-Ray Flare That Rises from a Very Low Background Level in the GOES Data.- 5.3.3.4. A Major Coronal Mass Ejection with no Detectable X-Ray Flare.- 5.3.3.5 What, Then, is the Origin of Coronal Mass Ejections?.- 5.4 Summary.- 6. Preflare Activity.- 6.1 General Activity in Active Regions.- 6.2 Precursors to Major Flares.- 6.2.1 UV Emission.- 6.2.2 Soft X-Rays.- 6.2.3 Preflare Radio Emission.- 6.3 Chromospheric Evaporation.- 6.4 The Onset of Coronal Mass Ejections.- 6.5 Surges.- 6.6 Conclusions.- 7. Particle Acceleration in Flares.- 7.1 The “Pre-SMM” Paradigm.- 7.2 High-Energy Flare Observations.- 7.2.1 Temporal Phenomena.- 7.2.1.1 Rapid Acceleration to Very High Energies.- 7.2.1.2 Rapid X-Ray Variations.- 7.2.1.3 Energy-Dependent Delays.- 7.2.2 Properties of Interacting Particles.- 7.2.2.1 Electron Spectra.- 7.2.2.2 Ion Spectra.- 7.2.2.3 Electron/Proton Ratio.- 7.2.3 Interplanetary Particles and Interacting Particles.- 7.2.4 Is There a Threshold for Particle Acceleration?.- 7.2.5 Geometry of the Interaction Region.- 7.2.5.1 Directivity.- 7.2.5.2 Height and Extent of Interaction Region.- 7.2.6 Very-High-Energy Phenomena.- 7.2.6.1 Energetic Solar Neutrons.- 7.2.6.2 High-Energy Photons.- 7.3 Mechanisms for Particle Acceleration.- 7.3.1 Stochastic Acceleration.- 7.3.2 Shock Acceleration.- 7.3.3 Direct Acceleration by DC Electric Fields.- 7.4 Summary.- 8. Nonthermal Flare Emissions.- 8.1 Statistical Aspects of Hard X-Ray Flares.- 8.1.1 Variability during the Solar Activity Cycle.- 8.1.2 Periodicities during the Solar Activity Cycle.- 8.1.3 Frequency Distributions and Correlations.- 8.1.4 The Concept of Self-Organized Criticality.- 8.2 Particle Acceleration and Injection.- 8.2.1 Fast Time Structures in Hard X-Rays.- 8.2.2 The Concept of a “Statistical Flare”.- 8.2.3 Electron Beam Signatures in Hard X-Rays and Radio.- 8.2.4 Pulsed Injection of Particles.- 8.2.5 Second-Step Acceleration.- 8.3 Particle Trapping and Precipitation.- 8.3.1 Incoherent Radiation from Trapped Particles.- 8.3.1.1 Temporal Aspects.- 8.3.1.2 Spectral Analysis.- 8.3.1.3 Imaging Data.- 8.3.2 Coherent Emission from Trapped Particles.- 8.3.2.1 Beam-Driven Emission in the Trap.- 8.3.2.2 Loss-Cone-Driven Emission.- 8.3.3 Pulsation Mechanisms in the Trap.- 8.3.4 Precipitation Signatures.- 8.4 Flare Diagnostics from Hard X-Ray/Radio Observations.- 9. Chromospheric Evaporation Theory.- 9.1 Pre-SMM Results.- 9.1.1 Early Observations.- 9.1.2 Theories prior to SMM.- 9.1.3 P78-1 Observations.- 9.2 Early SMM Results.- 9.2.1 Initial SMM Observations of Soft X-Ray Line Profiles.- 9.2.2 Hinotori Observations.- 9.2.3 Theories after Initial SMM Observations.- 9.2.3.1 Thermal Models.- 9.2.3.2 Nonthermal Model.- 9.2.3.3 Other Models.- 9.2.4 Combined SMM X-Ray and H? Observations.- 9.3 Later SMM Results.- 9.3.1 Later SMM Observations of Soft X-Ray Line Profiles.- 9.3.2 Other Wavelengths.- 9.3.3 Recent Theories.- 9.4 Future Developments.- 9.5 Conclusions.- 10. Flare Dynamics.- 10.1 Results from Soft X-Ray Spectra.- 10.1.1 Physical Properties of the Flare Plasmas.- 10.1.1.1 Electron Temperature Measurements.- 10.1.1.2 Temperature Distribution of the Flare Plasma.- 10.1.1.3 Density Measurements.- 10.1.1.4 Departures from Ionization Equilibrium.- 10.1.2 Dynamics.- 10.1.2.1 Impulsive-Phase X-Ray Line Profiles.- 10.1.2.2 Analysis Techniques for Soft X-Ray Spectra.- 10.2 Chromospheric Evaporation.- 10.2.1 Properties of Plasma Upflows.- 10.2.1.1 Blueshifted Spectral Emission.- 10.2.1.2 Velocity-Temperature Distribution of Convective Flows.- 10.2.1.3 Upflows during the Cooling Phase.- 10.2.1.4 Soft and Hard X-Ray Imaging Observations.- 10.2.2 Energetics of Chromospheric Evaporation.- 10.2.2.1 Mass and Energy Balance as Deduced from Soft X-Rays.- 10.2.2.2 Results of Coordinated H? and X-Ray Observations.- 10.2.3 Simulations of the Hydrodynamics of Flare Loops.- 10.2,3.1 Model Equations.- 10.2.3.2 Numerical Design Issues.- 10.2.3.3 Results of Modeling.- 10.2.4 Simulations of the Soft X-Ray Spectral Emission.- 10.2.4.1 Results on the Dynamics from Simulated Line Profiles.- 10.2.4.2 Simulations of the Average Properties of the Evaporated Plasma.- 10.2.4.3 Constraints on Flare Models from Impulsive-Phase Spectra.- 10.3 Nature of Nonthermal Line Broadenings.- 10.3.1 Properties of Nonthermal Broadenings.- 10.3.1.1 Determination of vnt.- 10.3.2 Broadening Mechanisms.- 10.3.3 Interpretations of the Observations.- 10.3.4 Line Broadening as a Signature of Magnetic Reconnection.- 10.3.4.1 Models of RCSs and Suprathermal Line Profiles.- 10.4 Concluding Remarks.- 11. Ultraviolet Flare Studies.- 11.1 UV Flare Plasma Diagnostics.- 11.2 UV and Hard X-Ray Bursts.- 11.3 Flare Topology: Interacting Loops.- 11.4 Discussion.- 12. The Gradual Phase of Flares.- 12.1 Heating and Cooling in the Gradual Phase.- 12.2 Emission Measure-Temperature Diagrams.- 12.3 Flaring Arches.- 12.4 Gradual Phase of Eruptive Flares.- 12.5 Postflare Giant Arches.- 12.6 Giant Arches: Modeling and Interpretation.- 13. Spectroscopy and Atomic Physics.- 13.1 Theory of Line Intensities.- 13.2 Density-Sensitive Line Ratios.- 13.3 Temperature-Sensitive Line Ratios.- 13.4 Element Abundances.- 13.5 Photospheric X-Ray Lines.- 13.6 Checking and Correcting Atomic Data.- 13.7 Summary and Future Directions.- 14. Solar-Terrestrial and Terrestrial Science.- 14.1 SMM’s Impact on Solar-Terrestrial Studies.- 14.1.1 Paradigm Shift in Solar-Terrestrial Physics.- 14.1.2 Two Classes of SEP Events.- 14.2 ?-Rays from the Earth.- 14.2.1 Galactic Cosmic Ray-Induced ?-Rays from the Earth.- 14.2.2 Solar Cosmic Ray-Induced ?-Rays from the Earth.- 14.3 Transient Radiation Belts from Orbiting Nuclear Reactors.- 14.4 Mesospheric Chemistry Studies with UVSP.- 14.4.1 Ozone Measurements.- 14.4.2 Molecular Oxygen Measurements.- 15. Solar-Stellar Connection.- 15.1 Stellar Coronae and Acoustic Heating.- 15.2 The Dividing Line.- 15.3 The Rotation-Activity Relation: Calibrating the Dynamo.- 15.4 Age versus Activity: The Evolution of the Sun.- 15.5 Stellar Activity Cycles.- 15.6 Mapping Stellar Surfaces.- 15.7 Flares on Other Stars.- 15.8 What is the Range of Stellar Power Ratios?.- 15.9 Conclusion.- 16. Comet Observations.- 16.1 Comet Halley and Comet Machholz.- 16.2 Comet Machholz (1988 XV).- 16.3 Kreutz Family of Sungrazing Comets.- 16.4 Summary.- 17. Cosmic Studies.- 17.1 Hard X-Ray Sources.- 17.1.1 A0535+26.- 17.1.2 Cygnus X-1.- 17.1.3 HXRBS Studies of Galactic Hard X-Ray Sources.- 17.2 ?-Ray Bursts.- 17.2.1 Spectra.- 17.2.2 Spectral Evolution.- 17.2.3 Periodicities.- 17.2.4 Statistical Studies.- 17.2.5 Soft ?-Ray Repeaters.- 17.3 ?-Ray Observations of Recent Supernovae.- 17.3.1 Discovery of ?-Rays from SN1987a.- 17.3.2 Limits on 56Ni Production in a Type I Supernova.- 17.4 ?-Ray Observations of Recent Novae.- 17.5 Searches for ?-Ray Transients.- 17.5.1 ?-Ray Lines from SS433.- 17.5.2 Search for Short Annihilation Line Transients.- 17.5.3 Search for Transient Lines from the Crab Nebula.- 17.5.4 Narrow or Moderately Broadened Transient Lines.- 17.5.5 Transient Emissions from Relativistic-Pair Plasmas.- 17.6 Galactic Observations.- 17.6.1 Observations of Interstellar 26Al.- 17.6.2 Galactic Positron Annihilation Radiation.- 17.6.3 The Diffuse Galactic Spectrum from 0.3 to 8.5 MeV.- 17.6.4 Limits on Galactic 44Ti and 60Fe.- 17.6.5 Limits on Deexcitation Lines from Interstellar Carbon and Oxygen.- 17.6.6 Neutron Capture in Black Hole Candidates.- 17.7 Summary of ?-Ray Line Observations.- References.- Acronyms.- Acknowledgment of Copyright.