This book is the first part of the originally planned publication by Z. Svestka and L. D. de Feiter 'Solar High Energy Photon and Particle Emission'. The second part, with the original title, was to be published by de Feiter in about one year from now. However, to the deep sorrow of all of us, Dr de Feiter died suddenly and unexpectedly when the present book was in print. Thus, unfortunately, de Feiter's second part may not appear. Due to the fact that the originally planned publication was divided into two parts, the present book is mainly descriptive and concerned with the flare morphology. It was expected that theoretical interpretations would be extensively developed in the second part, prepared by de Feiter. In particular, this refers to the theoretical back­ grounds of radio emissions, particle acceleration and particle propagation in space. Only in Chapter II, concerning the 'low-temperature' flare, do we go deeper into the theoretical interpretations, anticipating that de Feiter would have been concerned mainly with the 'high-energy' physics. Still, the book includes discussions on all important aspects of flares and thus can present the reader with a complete picture of the complex flare phenomenon. It is clear that many observed data on flares can be interpreted in different ways.

Inhalt

I. Introduction.- II. The Low-Temperature Flare.- 2.1. Flare Observations in the H? Line.- 2.1.1. The Flare Importance.- 2.1.2. Flares in Relation to Magnetic Fields.- A. Flare Positions Relative to Sunspots and Plages.- B. Flare Positions in the Magnetic Field.- C. Flare-Associated Changes in the Magnetic Field.- C.l. Old-Type Measurements.- C.2. High-Resolution Measurements.- C.3. Mathematical Models of Coronal Magnetic Fields.- C.4. Other Methods.- C.5. Summary.- 2.1.3. Motions in Flares.- A. Slow Ascent.- B. Rise and Fall.- C. High-Speed Ejections.- D. Rotation Effects.- E. Expansion of Flare Ribbons.- F. Fast Expansion.- G. In-Fall Motions.- 2.2. Flare Spectra.- 2.2.1. Characteristic Features of the Flare Spectrum.- 2.2.2. Method of Analysis of Hydrogen Lines.- 2.2.3. Line Broadening.- 2.2.4. Electron Density.- A. Electron Density in Disc Flares.- B. Electron Density in Limb Flares.- 2.2.5. The Optical Thickness.- 2.2.6. Electron Temperature.- 2.2.7. The Filamentary Structure of Flares.- 2.2.8. Hydrogen Density.- 2.2.9. Line Asymmetry.- 2.2.10. Differences between Prominences and Limb Flares.- 2.2.11. Continuous Emission.- A. Synchrotron Radiation.- B. Particle Penetration to Low Atmospheric Layers.- C. Heating of Upper Photosphere.- D. White-Light Flare Wave.- 2.3. Models of Chromospheric Flares.- 2.3.1. Models of Energy Transfer from the Corona.- A. Brown's Model.- B. Model by Shmeleva and Syrovatsky.- C. Models Including both Conduction and Particle Heating.- D. Models by Canfield and Athay.- 2.3.2. Model by Machado and Linsky.- A. The Photospheric Flare.- B. The Chromospheric Flare.- III. The High-Temperature Flare.- 3.1. Thermal Phenomena.- 3.1.1. Coronal Condensations.- 3.1.2. Soft X-Ray Emission.- A. Soft X-Ray Bursts.- B. X-Ray Flares.- C. Indirect Observations of Solar X-Rays.- 3.1.3. Flare Spectrum in the X-Ray Region.- A. The Continuous Emission.- B. The Line Emission.- 3.1.4. Temperature in the X-Ray Flare.- A. Temperature and Emission Measure.- B. Line Excitation.- C. Flare Cooling.- 3.1.5. Electron Density in the X-Ray Flare.- 3.1.6. Gradual Microwave Bursts.- 3.2. Non-Thermal Phenomena.- 3.2.1. Hard X-Ray Bursts.- A. Characteristic Properties of the Hard X-Ray Bursts.- B. Evidence on the Non-Thermal Nature of the Hard X-Ray Bursts.- C. Theoretical Interpretation of the Hard X-Ray Bursts.- D. Models of Impulsive and Continuous Acceleration.- E. Thin-Target and Thick-Target Emission.- 3.2.2. EUV Bursts.- 3.2.3. Impulsive Microwave Bursts.- A. Characteristic Properties.- B. Interpretation of the Impulsive Microwave Bursts.- C. Controversy with the Theory of Hard X-Ray Bursts.- 3.2.4. Type IV Bursts.- A. Type IVmA Bursts.- B. Type IVmB Bursts.- C. Type IVdm Bursts and Radio Pulsations.- D. Type IV Burst Spectrum.- 3.2.5. Type II Bursts.- 3.2.6. Type III Bursts.- A. Type III Burst Occurrence.- B. Properties of Type III Bursts.- C. Interpretation of Type III Bursts.- D. Type U Bursts.- E. Type V Bursts.- IV. Flare-Associated Optical Phenomena.- 4.1. Pre-Flare Filament Activation.- 4.2. Surges and Sprays.- 4.2.1. Surges.- 4.2.2. Sprays.- 4.3. Flare Waves.- 4.3.1. The Wave Fronts.- 4.3.2. Disparitions Brusques.- 4.4. Loop Prominences.- V. Particle Emission from Solar Flares.- 5.1. Solar Protons.- 5.1.1. Cosmic-Ray and Proton Flares.- A. Characteristics of the Flare on the Sun.- B. Characteristics of the Active Region.- C. Complexes of Activity.- D. Time Variations in the Proton Flare Occurrence.- 5.1.2. Satellite-Sensed Events.- 5.1.3. The Energy Spectrum.- A. The Propagation Effects.- B. The Storage Effects.- C. The Size of an Event.- 5.2. Heavier Nuclei.- 5.3. Solar Electrons.- 5.3.1. Non-Relativistic Electrons.- A. The Event Occurrence and the Associated Flares.- B. Proton-Electron and Pure Electron Events.- C. Time of Acceleration.- 5.3.2. Relativistic Electrons.- 5.4. Nuclear Reactions in Flares.- 5.4.1. Accelerated Isotopes of Hydrogen and Helium.- 5.4.2. Neutrons.- 5.4.3. ?-Rays.- 5.5. Particle Clouds and Interplanetary Shock Waves.- 5.5.1. Characteristic Properties of Interplanetary Shocks.- 5.5.2. Shock-Wave-Associated Variations in the Particle Flux.- 5.5.3. Increased Helium Content behind Interplanetary Shock Waves.- VI. Flare Models.- 6.1. Basic Properties of Flares.- 6.2. Synthesis of a Flare.- A. Pre-Flare Phase.- B. Quasi-Thermal Flare.- C. Impulsive Flare.- D. Electron Flare.- E. Proton Flare.- F. Problems.- 6.3. The Energy Source.- 6.4. The Energy Storage.- 6.4.1. Alfvén Waves as the Source of Flares.- 6.4.2. Models with a Passive Role for the Magnetic Field.- A. Elliot's Model.- B. Schatzman's Model.- C. Carmichael's Model.- D. Pneuman's Model.- E. Model by Sen and White.- 6.4.3. Models with an Active Role for the Magnetic Field.- A. Model by Gold and Hoyle.- B. Model by Alfvén and Carlqvist.- C. Sheared Fields.- D. Force-Free Flare Build-up.- E. Current Sheets.- 6.5. The Energy Release.- 6.5.1. Models without a Current Sheet.- A. Piddington's Model.- B. Elliot's Model.- C. Kahler and Kreplin's Model.- D. Evaporating Flare Models.- E. Alfvén and Carlqvist's Model.- 6.5.2. Current Sheet Models.- A. Priest and Heyvaerts' Model.- B. Sturrock's Model.- C. Similarities with Magnetospheric Substorms.- D. Pustilnik's Model.- 6.5.3. Syrovatsky's Model.- A. The Pre-Flare Activation.- B. The Thermal Phase.- C. The impulsive Phase.- D. Deficiencies of Syrovatsky's Theory.- 6.6. The Particle Acceleration.- 6.6.1. Current Interruption.- 6.6.2. Fermi Mechanism.- 6.6.3. Stochastic Acceleration.- References.- Index of Subjects.