Physics of the Inner Heliosphere I

1. Introduction.- 1.1 Why the "Inner Heliosphere"?.- 1.2 Scientific Objectives and General Aspects of the Helios Mission.- 1.3 Scientific Highlights and Summary.- 1.4 Heliospheric Physics and Some Astrophysical Connections.- References.- 2. Remote Sensing Observations of the Solar Corona.- 2.1 Introduction.- 2.2 Morphology of the Outer Corona: A Brief Survey.- 2.2.1 The White-Light Corona.- 2.2.2 Sources and Properties of Coronal Emission.- 2.2.3 Coronal Rotation.- 2.3 Coronal Plasma Density.- 2.3.1 Spatial Distribution of Coronal Plasma Density.- 2.3.2 Temporal Variations.- 2.4 Coronal Magnetic Structure.- 2.4.1 Coronal Magnetic Field Models.- 2.4.2 Coronal Magnetic Field Observations.- 2.5 Coronal Velocities and Turbulence.- 2.5.1 EUV Observations.- 2.5.2 Radio-Sounding Observations.- 2.6 Coronal Mass Ejections.- 2.6.1 CME Morphology, Phenomenology and Statistics.- 2.6.2 Radio-Sounding Investigations of Coronal and Interplanetary Transients.- 2.7 Appendix: Radio-Sounding Measurement Techniques.- References.- 3. Large-Scale Structure of the Interplanetary Medium.- 3.1 Introduction.- 3.1.1 The Solar Wind at 1 AU, Status 1974.- 3.1.2 The Plasma Experiment on the Helios Probes.- 3.1.3 The Basic Stream Structure.- 3.2 Longitudinal Stream Boundaries.- 3.2.1 Radial Evolution of High-Speed Stream Fronts.- 3.2.2 Stream Interfaces.- 3.2.3 Fine Structure of High-Speed Stream Fronts.- 3.2.4 Problems of Mapping Solar Wind Structures Back to the Sun.- 3.2.5 Mapping and Predictions.- 3.2.6 A Scenario of Longitudinal Stream Structure.- 3.3 Latitudinal Stream Boundaries.- 3.3.1 Local Latitudinal Speed Gradients.- 3.3.2 Evidence for Meridional "Squeezing" of Interaction Regions.- 3.3.3 Problems of Associating Stream Profiles from Different Latitudes.- 3.3.4 A Scenario of Latitudinal Stream Structure.- 3.4 Stream Structures with Respect to the Heliomagnetic Equator.- 3.4.1 Stream Structure with Respect to Heliomagnetic Latitude.- 3.4.2 Stream Structure with Respect to Heliomagnetic Longitude.- 3.4.3 Solar Wind and Coronal Streamers.- 3.4.4 Interplanetary Consequences.- 3.5 Corotating Shock Waves.- 3.6 Scenario in Terms of the "Ballerina Model".- 3.7 The Solar Wind as a Two-State Phenomenon.- 3.7.1 Slow and Fast Solar Wind: Characteristic Differences.- 3.7.2 Slow and Fast Solar Wind: Similarities.- 3.7.3 Radial Gradients.- 3.8 Variations During the Solar Activity Cycle.- 3.8.1 Variations of the "Average" Solar Wind in the Ecliptic Plane.- 3.8.2 Structural Changes During the Solar Cycle.- 3.9 Conclusions and Outlook.- 3.9.1 Solar Wind Origin.- 3.9.2 Other Open Questions on Large-Scale Phenomena.- 3.9.3 Outlook.- References.- 4. The Interplanetary Magnetic Field.- 4.1 Introduction.- 4.1.1 The Magnetic Field at 1 AU, Status 1974.- 4.1.2 A Short Description of the Helios Magnetic Experiments.- 4.2 Radial Variations.- 4.2.1 Background.- 4.2.2 The Radial Component Br.- 4.2.3 The Azimuthal Component B?.- 4.2.4 The Normal Component B?.- 4.2.5 The Field Magnitude B.- 4.2.6 The Field Orientation.- 4.2.7 The Field Variability at Low Frequencies.- 4.3 The Solar Magnetic Field and the Interplanetary Magnetic Field.- 4.3.1 Background Observations.- 4.3.2 The Heliospheric Current Sheet.- 4.3.3 The Source Region of the Heliospheric Current Sheet.- 4.3.4 The Fine Structure of the Sector Boundary.- 4.4 Summary and Outlook.- References.- 5. Interplanetary Dust.- 5.1 Introduction.- 5.2 Methods of Observation.- 5.2.1 Collection of Individual Particles.- 5.2.2 Impact Ionization Detectors.- 5.2.3 Penetration Detectors.- 5.2.4 Lunar Microcraters.- 5.2.5 Meteors.- 5.2.6 Zodiacal Light Observations.- 5.2.7 Comparison.- 5.3 Particle Properties.- 5.3.1 Elemental Composition.- 5.3.2 Shape.- 5.3.3 Optical Properties.- 5.3.4 Density.- 5.4 Physical Processes.- 5.4.1 Gravity.- 5.4.2 Radiation Pressure.- 5.4.3 The Poynting-Robertson Effect.- 5.4.4 The Lorentz Force.- 5.4.5 Evaporation.- 5.4.6 Sputtering.- 5.4.7 Collisions.- 5.5 Mass and Size Distribution.- 5.5.1 Particle Populations.- 5.5.2 Spatial Density.- 5.5.3 ? Meteoroids and the Discussion About Small Particles in Interplanetary Space.- 5.5.4 Mass Influx.- 5.6 Spatial Distribution.- 5.6.1 Symmetries.- 5.6.2 Out-of-ecliptic Distribution.- 5.6.3 Radial Dependence.- 5.7 Orbit Distribution.- 5.7.1 Meteor Orbits.- 5.7.2 Orbits Determined from Zodiacal Light Observations.- 5.7.3 Orbits of Small Meteoroids.- 5.8 Compatibility of Dust Experiments with Zodiacal Light Observations.- 5.9 Sources and Sinks.- 5.9.1 Asteroids as Sources of Dust.- 5.9.2 Dust Production by Comets.- 5.9.3 Cometary Dust.- 5.9.4 Input and Spatial Distribution - the Formal Relation.- 5.9.5 Input and Spatial Distribution - Consequences.- 5.9.6 Mass Balance on a Large Scale.- 5.9.7 Local Mass Balance.- 5.10 Attempt at a Judgement.- References.