Introduction to Solar Radio Astronomy and Radio Physics

ISBN-13: 9789027709974 / Angielski / Miękka / 1979 / 332 str.

A. Kruger

Opis

1. 1. Short History of Solar Radio Astronomy Since its birth in the forties of our century, solar radio astronomy has grown into an extensive scientific branch comprising a number of quite different topics covering technical sciences, astrophysics, plasma physics, solar-terrestrial physics, and other disciplines. Historically, the story of radio astronomy goes back to the times of James Clerk Maxwell, whose well known phenomenological electromagnetic field equations have become the basis of present-time radio physics. As a direct consequence of these equations, Maxwell was able to prognosticate the existence of radio waves which fifteen years later were experimentally detected by the famous work of Heinrich Hertz (1887/88). However, all attempts to detect radio waves from cosmic objects failed until 1932, which was mainly due to the early stage of development of receiving techniques and the as yet missing knowledge of the existence of a screening ionosphere (which was detected in 1925). Therefore, famous inventors like Thomas Edison and A. E. Kennelly, as well as Sir Oliver Lodge, were unsuccessful in receiving any radio emission from the Sun or other extraterrestrial sources. Another hindering point was that nobody could a priori expect that solar radio emission should have something to do with solar activity so that unfortunately by chance some experiments were carried out just at periods of low solar activity. This was also why Karl Guthe Jansky at the birth of radio astronomy detected galactic radio waves but no emission from the Sun.

Spis treści

I Introduction.- 1.1. Short History of Solar Radio Astronomy.- 1.2. General Views of the Sun.- 1.2.1. The Sun as a Source of Radio Waves.- 1.2.2. The Solar Atmosphere.- a. Photosphere.- b. Chromosphere.- c. Corona.- 1.2.3. Solar Activity.- a. General Phenomena.- b. Sunspots.- c. Plages.- d. Flares.- e. Prominences.- f. Active Longitudes, Sector Structure and Coronal Holes.- 1.3. Some Astronomical Fundamentals.- 1.3.1. Sun—Earth Distance.- 1.3.2. Coordinate Systems.- a. Horizontal System.- b. Equatorial System.- c. Solar Coordinates.- II Instrumental Background.- 2.1. Fundamentals of Radio Observations.- 2.1.1. The Electromagnetic Spectrum and the Atmospheric Radio Window.- 2.1.2. Radiation Quantities.- 2.2. Radio Telescope Aerials.- 2.2.1. Fundamental Aerial Parameters.- a. Aerial Patterns.- b. Effective Area and Gain.- c. Effective Aerial Temperature.- 2.2.2. Basic Types of Aerials.- a. Primary Antennas.- b. Reflectors.- c. Special Constructions.- 2.3. Radio Astronomy Receivers.- 2.3.1. Fundamental Receiver Parameters.- 2.3.2 Basic Types of Receivers.- a. General Principles.- b. Low-Noise Amplifiers.- 2.4. Polarization Measurements.- 2.4.1. Fundamentals of Polarized Radiation.- 2.4.2. Polarimeters.- 2.5. Absolute Calibration Experiments.- 2.5.1. General Aspects.- 2.5.2. Standard-Radiometer and Standard-Field Methods.- 2.6. Spectrography.- 2.6.1. Swept-Frequency Spectrographs.- 2.6.2. Multi-Channel Spectrographs.- 2.7 Interferometry and Heliography.- 2.7.1. Two-Element (Adding) Interferometers.- 2.7.2. Phase-Switched (Multiplying) Interferometers.- 2.7.3. Swept-Lobe Interferometers.- 2.7.4. Special Arrangements.- a. Receipt of Polarization.- b. Swept-Frequency Interferometer.- c. Wide-Band Interferometry.- d. Long-Baseline and Very-Long-Baseline Interferometry.- 2.7.5. The Grating (Multielement) Interferometer.- 2.7.6. Cross-Type Interferometers.- 2.7.7. Heliographs.- 2.8. Aperture-Synthesis Methods.- 2.8.1. General Principle.- III Phenomenology of Solar Radio Emission.- 3.1. The ‘Quiet’ Sun.- 3.1.1. Spectrum.- 3.1.2. Brightness Distribution.- 3.1.3. Model Calculations.- 3.1.4. The Basic Component of Solar Radio Emission.- 3.1.5. Exploration of the Outer Corona.- 3.1.6. About Solar Line Emissions.- 3.2. The Slowly Varying Component.- 3.2.1. General.- 3.2.2. Total Flux Characteristics.- 3.2.3. The Source Regions.- a. Observations.- b. Interpretation.- 3.2.4. Connection with X-Rays and Other Phenomena.- 3.2.5. Quasi-Periodic Oscillations.- 3.2.6. Large-Scale Patterns.- 3.3. Solar Continuum Bursts (a): Microwave Bursts.- 3.3.1. General Remarks.- 3.3.2. Morphology.- 3.3.3. Spectral Characteristics.- 3.3.4. Polarization and Source Structures.- 3.3.5. Association with Other Phenomena and Models.- 3.4. Fast-Drift Bursts.- 3.4.1. General Properties.- 3.4.2. Forms of Appearance (Gross Structure).- a. The ‘Standard’ Type III Burst.- b. U-Type Bursts.- c. J-Type Bursts.- d. Type V Bursts.- 3.4.3. Fine-Structure Emissions.- a. Stria Bursts (Split-Pair and Triple Bursts), Type IIIb Bursts.- b. Drift-Pair Bursts.- c. Thread-Like Patterns and Shadow-Type III Bursts.- d. Herring-Bone Structures.- e. Type III Storm Bursts.- 3.4.4. Ground-Based Observational Characteristics of Standard Type III Bursts.- a. Spectral Characteristics and Harmonic Structure.- b. Localization.- c. Morphology.- d. Polarization.- e. Associated Phenomena.- 3.4.5. Space Observations.- a. Short History.- b. Hectometer Fast-Drift Bursts.- c. Directivity.- d. Exciter Paths and Ray Trajectories.- 3.4.6. Interpretation.- a. The Exciter Source.- b. The Plasma-Wave Source.- c. The Radio-Wave Source.- d. Radio-Wave Propagation.- 3.5. Slow-Drift Bursts.- 3.5.1. General Observational Features.- a. Main Characteristics, Frequency Drift.- b. Morphology and Other Properties.- c. Heliographic Observations.- d. Associated Phenomena.- 3.5.2. Spectral Structure.- a. Harmonic Radiation.- b. Frequency Splitting.- c. Herring-Bone Structure.- 3.5.3. Interpretation.- a. History.- b. Type II Burst Models.- c. Shock-Wave Propagation.- d. Electromagnetic Radiation.- 3.6. Continuum Bursts (b): The Type IV Burst Complex.- 3.6.1. Introductory Remarks.- a. General Features.- b. Brief History.- c. Classifications.- d. Outline of a Complete Picture.- 3.6.2. The cm- and dm-Region.- a. Type IV? Bursts.- b. Type IVdm Bursts.- 3.6.3. The m-and Dm-Region.- a. Flare Continua (Quasi-Stationary Type IVm Bursts).- b. Moving Type IV Bursts (‘IVmA’).- c. Stationary Type IV Bursts (‘IVmB’).- 3.6.4. Type IV Burst Models.- a. Source Geometry.- b. Emission Processes.- 3.7. Noise Storms.- 3.7.1. Outline of the Phenomenon.- a. General Properties.- b. Related Phenomena.- 3.7.2. Storm Continua.- a. Phenomenological Characteristics.- b. Relation to Small-Band Features.- 3.7.3. Type I Bursts.- a. Basic Characteristics.- b. Chains of Type I Bursts.- c. Attempts at Interpretation.- 3.7.4. Type III Storms.- a. The Phenomenon.- b. Implications.- 3.8. Solar Radio Pulsations.- 3.8.1. General Features.- 3.8.2. Periodicities in the cm- and dm-Burst Radiation.- 3.8.3. Fine Structure and Short-Period Fluctuations in Type IV Bursts.- a. Pulsating Structures in the m-Region.- b. Parallel Drifting Bands (Zebra Patterns) and Groups of Tadpole Bursts.- 3.8.4. Medium-Period Fluctuations in Type IVmB Bursts and Noise Storms.- 3.8.5. Interpretations.- a. Modulation of Plasma Parameters.- b. Particle Ejections152 3.9. Summary.- IV Theory of Solar Radio Emission.- 4.1. Basic Properties of the Solar Atmosphere as a Plasma Medium.- 4.1.1. Compilation of Important Plasma Parameters.- 4.1.2. Density and Temperature.- a. Electron Density.- b. Thermal Equilibrium.- c. Nonthermal Energy Distributions.- 4.1.3. Magnetic Field.- a. Empirical Distributions.- b. Models.- c. Alfvén-Wave Velocity.- 4.1.4. Characteristic Time Scales and Transport Quantities.- a. Redistribution and Diffusion Times.- b. Electric and Heat Conductivity.- 4.2. Fundamentals of the Emission and Propagation of Radio Waves.- 4.2.1. Elementary Processes of the Generation of Radio Waves.- a. General Remarks and Definitions.- b. Primary Emission and Absorption Processes.- c. Indirect Emission and Absorption Processes.- 4.2.2. Basic Theoretical Developments.- 4.2.3. Polarized Radiation in a Plasma.- a. Basic Definitions.- b. Polarization of Radio Waves.- c. Faraday Effect.- 4.2.4. Propagation of Radio Waves.- a. Ray Trajectories - Refraction and Scattering.- b. Dispersion Relations.- c. Radiative Transfer.- 4.3. Single-Particle Approximation: An Account of Direct Radio Emission Mechanisms.- 4.3.1. Coulomb Bremsstrahlung.- a. Thermal Free-Free Emission and Absorption.- b. Influence of External Magnetic Fields, Polarization Effects.- c. Nonthermal Bremsstrahlung Effects.- 4.3.2. Cyclotron (Gyro-Synchrotron) Emission.- a. The Emission Equation.- b. Basic Formulas.- c. Correction Terms.- 4.3.3. Time Dependencies of Radiation.- 4.4. Cold-Plasma Approximation: Some Aspects of Synchrotron Radiation and Cerenkov Radiation.- 4.4.1. Magneto-Ionic Theory.- 4.4.2. Synchrotron Radiation.- a. Ultra-Relativistic Approximation.- b. Polarization.- c. Influence of the Plasma Medium, Razin Effect.- d. Synchrotron Reabsorption.- e. Relations Between the Particle-Energy Spectrum and the Synchrotron-Radiation Spectrum.- 4.4.3. The Cerenkov Effect.- 4.5. Warm-Plasma Effects: Gyroresonance Absorption and Plasma Waves.- 4.5.1. Kinetic Theory.- a. Introductory Remarks.- b. The Boltzmann—Vlasov Equation.- 4.5.2. Electromagnetic Gyroresonance Absorption.- 4.5.3. General Aspects of Radiation in a Turbulent Plasma.- 4.5.4. Longitudinal Plasma Waves.- a. Plasma Waves in an Isotropic Medium (Langmuir Waves).- b. Cyclotron-Harmonic Waves (Bernstein Waves).- 4.5.5. Hydromagnetic Waves.- 4.5.6. Summary of Warm-Plasma Wave Modes.- 4.6. Wave-Mode Transformations: Wave-Particle and Wave-Wave Interactions.- 4.6.1. Scattering by Thermal and Superthermal Particles.- a. General Cases.- b. Differential Scattering Within Individual Wave Modes.- 4.6.2. Interactions of Different Wave Modes.- 4.6.3. Some Possible Solar Radio Applications.- 4.7. Instabilities and Coherent Emission.- 4.7.1. General Concepts.- 4.7.2. Classifications of Plasma Instabilities.- 4.7.3. Some Important Instabilities.- a. Two-Stream Instabilities.- b. Velocity-Anisotropy Instabilities.- c. Tearing-Mode Instabilities.- 4.7.4. Amplification of Electromagnetic Waves.- a. Negative Absorption of Radio Waves.- b. Induced Scattering of Coherently Generated Plasma Waves.- V Integration of Radio Astronomy into Solar and Solar-Terrestrial Physics.- 5.1. Estimation of Solar Plasma Parameters.- 5.1.1. Particle Density and Magnetic Field.- 5.1.2. Energy Content.- 5.2. The Flare Phenomenon.- 5.2.1. The Low-Temperature Flare.- 5.2.2. The High-Temperature Flare.- 5.2.3. The High-Energy Flare.- 5.3. Particle Acceleration and Energy Release.- 5.3.1. Acceleration Mechanisms.- a. General Concepts.- b. Acceleration by Electric Fields.- c. The Fermi-Parker Mechanism.- d. Other Electromagnetic Acceleration Mechanisms.- 5.3.2. Energy Release by Different Modes of Plasma Turbulence.- 5.3.3. Relation Between Electron Energy Spectrum and Emitted Photon Spectrum.- 5.4. Particle Radiation and Radio Waves.- 5.4.1. The Solar Wind.- 5.4.2. Electron Events.- a. Nonrelativistic Electrons.- b. Relativistic Electrons.- 5.4.3. Proton Events.- 5.5. Shock Waves and Magnetospheric Disturbances.- 5.5.1. Flare-Produced Interplanetary Shock Waves.- 5.2.2. Analogies Between Solar and Magnetospheric Processes.- 5.6. Burst Origin and Flare Theories.- 5.6.1. Basic Problems.- a. The Energy/Time Problem.- b. The Mass Problem.- c. The Spatial Communication Problem.- 5.6.2. Possible Sources of the Flare Energy.- a. Energy Storage by Particles and Nonelectromagnetic Force Fields.- b. Energy Transport by Hydromagnetic Waves.- c. Electromagnetic Flare Build-Up Processes.- 5.6.3. Energy Release in the Hydrodynamic Flare Stage.- a. Current Sheet Models (General).- b. Dynamic Magnetic Field Dissipation.- c. The Petschek Mechanism.- 5.6.4. Kinetic Stages of Flare-Energy Release.- a. Analogies to Laboratory Experiments.- b. Deficiencies of Previous Flare Theories.- 5.7. Summary and Prospects.- Literature.- List of Symbols.