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.

Physics of the Inner Heliosphere gives for the first time a comprehensive and complete summary of our knowledge of the inner solar system. Using data collected over more than 11 years by the HELIOS twin solar probes, one of the most successful ventures in unmanned space exploration, the authors have compiled 10 extensive reviews of the physical processes of the inner heliosphere and their connections to the solar atmosphere. Researchers and advanced students in space and plasma physics, astronomy, and solar physics will be surprised to see just how closely the heliosphere is tied to the sun and how sensitively it depends on our star. The four chapters of Volume I of the work deal with large-scale phenomena: - observations of the solar corona - the structure of the interplanetary medium - the interplanetary magnetic field - interplanetary dust.