Man, through intensive observations of natural phenomena, has learned about some of the basic principles which govern nature. The aurora is one of the most fascinating of these natural phenomena, and by studying it, man has just begun to comprehend auroral phenomena in terms of basic cosmic electrodynamic processes. The systematic and extensive observation of the aurora during and after the great international enterprise, the International Geophysical Year (lGY), led to the concept of the auroral substorm. Like many other geophysical phenomena, auroral displays have a dual time (universal- and local-time) dependence when seen by a ground-based observer. Thus, it was a difficult task for single observers, rotating with the Earth once a day, to grasp a transient feature of a large-scale auroral display. Such a complexity is inevitable in studying many geophysical features, in particular the polar upper atmospheric phenomena. However, it was found that their complexity began to unfold when the concept of the auroral substorm was introduced. In a book entitled Polar and Magnetospheric Substorms, the predeces sor to this book, I tried to describe the auroral phenomena as completely as possible in terms of the concept of the auroral substorm. At that time, the first satellite observations of particles and magnetic fields during substorms were just becoming available, and it was suggested that the auroral sub storm is a manifestation of a magnetospheric phenomenon called the magnetospheric substorm.

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1 Open Magnetosphere and the Auroral Oval.- 1.1. Open Magnetosphere.- 1.2. Auroral Oval.- 1.3. Open Magnetosphere and the Auroral Oval.- 1.3.1. Solar Energetic Particles and the Auroral Oval.- 1.3.2. Field-Aligned Currents and the Auroral Oval.- (a) Distribution of Field-Aligned Currents above the Polar Ionosphere.- (b) Field-Aligned Currents and Auroral Arcs.- 1.3.3. Field-Aligned Currents and Ionospheric Currents.- (a) Formulation.- (b) Model.- (c) Results.- 1.3.4. Electric Field Distribution and the Auroral Oval.- (a) Observations.- (b) Theoretical Studies.- 1.3.5. Plasma Convection in the Equatorial Plane and the Polar Cap.- (a) Observations.- (b) Theoretical Studies.- 1.3.6. Three-Dimensional Magnetospheric Current System.- (a) Fejer-Swift-Vasyliunas-Wolf (FSVW) Model.- (b) Boström-Rostoker (BR) Model.- 1.3.7. Sqp Variation and the Auroral Oval.- 1.4. Solar Wind Magnetosphere Dynamo.- 1.4.1. Electromotive Force and Power.- 1.4.2. Steady State Merging.- (a) Sweet-Parker's Model.- (b) Petschek's Model.- (c) Sonnerup's Model.- 1.4.3. Production Rate of the Open Flux.- References.- 2 Auroras and Auroral Particles.- 2.1. Introduction.- 2.1.1. Montage Photographs of the Auroral Oval.- 2.1.2. Schematic Distribution Pattern of Auroras.- 2.2. Auroras in Different Local Time Sectors.- 2.2.1. Discrete Auroras and Diffuse Auroras in the Night Sector.- 2.2.2. Midday Auroras.- 2.2.3. Polar Cap Auroras.- 2.3. Auroral Electrons: The Statistical Precipitation Pattern.- 2.4. Auroral Electrons: Spectra of Auroral Electrons.- 2.4.1. Evening and Midnight Sectors.- (a) Satellite Observations.- (b) Rocket Observations.- 2.4.2. Morning Sector.- 2.4.3. Noon (Cusp) Sector.- 2.4.4. Polar Cap.- 2.5. Auroral Electrons and Field-Aligned Currents.- 2.5.1. Satellite Observations.- 2.5.2. Rocket Observations.- 2.6. Auroral Particles and Atmospheric Emissions.- 2.7. Auroral Protons.- 2.8. Auroral Helium Ions (He++, He+) and Oxygen Ions (O+).- 2.8.1. Auroral Helium Ions.- 2.8.2. Auroral Oxygen Ions.- 2.9. Auroral Oval and the Polar Ionosphere.- 2.9.1. F Region.- 2.9.2. E Region.- 2.10. Summary.- References.- 3 Distribution of Plasmas in the Magnetosphere.- 3.1. Five Plasma Domains.- 3.2. Plasma Mantle.- 3.2.1. Frontal Region of the Magnetosphere.- 3.2.2. Magnetotail (X > -30 RE).- 3.2.3. Magnetotail at the Lunar Distance (X ? ?60 RE).- 3.2.4. Distant Magnetotail (X ~ ?500 ~ -1000 RE).- 3.3. Polar Cusp.- 3.4. Plasma Sheet.- 3.4.1. Plasma Sheet During Very Quiet Periods.- 3.4.2. Average Energy Characteristics.- (a) ?10 RE > X > ?30 RE.- (b) Plasma Sheet at the Lunar Distance (X ? ?60 RE).- 3.5. Origin and Dynamics of the Sheet Plasma.- 3.5.1. Meridional Convection of Magnetospheric Plasma.- 3.5.2. Electric Currents, Magnetic Field Structure and the Balance of Stresses in the Plasma Sheet.- (a) Two-Dimensional Maxwell-Vlasov and Macroscopic Approaches.- (b) Kinetic Approaches.- 3.6. Van Allen Belts.- 3.6.1. Ring Current Belt: the Quiet Time Belt.- 3.6.2. Electron Belt.- 3.7. Plasmasphere.- 3.8. Magnetospheric Plasmas and Auroral Particles.- 3.8.1. Oval Belt.- 3.8.2. Annular Belt.- 3.9. Acceleration Processes of Arc-Producing Auroral Electrons.- 3.9.1. Introduction.- 3.9.2. Auroral Arcs and Their Topological Relation with the Magnetospheric Structure.- 3.9.3. Arc Energization System.- 3.9.4. Possible Processes in the Wave-Particle Interaction Region.- (a) Current Driven Instabilities.- (b) Double Layer.- References.- 4 Responses of the Magnetosphere to Interplanetary Disturbances.- 4.1. Interplanetary Disturbances.- 4.2. Interplanetary Pressure Disturbances and Magnetospheric Responses.- 4.3. Changes of the IMF EW Component and Magnetospheric Responses.- 4.3.1. Merging of the Geomagnetic Field Lines with the IMF EW Component.- 4.3.2. Observations.- 4.4. Changes of the IMF NS Component and Magnetospheric Responses.- 4.4.1. Introduction.- 4.4.2. Merging with the IMF of an Arbitrary Angle.- 4.4.3. Erosion of the Dayside Magnetosphere.- (a) Magnetopause Motion.- (b) Cusp Motion.- 4.4.4. Magnetic Flux Transfer to the Magnetotail.- (a) High Latitude Lobe Field BT.- (b) Radius of the Magnetotail RT.- (c) Plasma Sheet Thinning.- 4.4.5. Enhanced Convection in the Plasma Sheet.- (a) Earthward Advance of the Plasma Sheet.- (b) Tendency Toward the Tail-Like Field.- (c) Slow Decrease of the H Component at the Synchronous Distance and in Low Latitudes.- 4.4.6. Polar Cap Phenomena.- (a) Dawn-to-Dusk Electric Field in the Polar Region.- (b) Expansion of the Auroral Oval.- (c) DP-2 Variation.- 4.4.7. Correlation Between Bs (= -Bz) and the AE Index.- (a) Arnoldy's Study of the Relationship between Bs and the AE Index.- (b) The AE Index.- 4.4.8. Summary.- References.- 5 Magnetospheric Substorms: Introduction.- 5.1. A New Classification of Magnetospheric Disturbances.- 5.1.1. Reversible or Quasi-Reversible Disturbances.- 5.1.2. Irreversible Disturbances.- 5.2. Substorm Energy ?? and Substorm Function ? = ?(?D).- 5.2.1. Ground State of the Magnetosphere.- 5.2.2. Substorm Function ? = ?(?D).- 5.3. Substorm Intensity.- 5.3.1. Kinetic Energy of Auroral Particles.- 5.3.2. Joule Heat Energy of the Auroral Electrojet.- 5.4. Time-Dependent Merging.- 5.4.1. Stability of the Plasma Sheet.- 5.4.2. Numerical Simulation of Reconnection.- 5.4.3. Plasma Processes.- 5.4.4. Substorm Time Constants.- 5.4.5. Short Review of Theories of the Magnetospheric Substorm.- 5.5. Magnetospheric Substorms.- 5.5.1. Neutral Line Formation Enhanced Reconnection or Plasma Sheet Deflation Enhanced Reconnection.- 5.5.2. Enhancement of the Auroral Oval Circuit Current.- 5.5.3. Penetration of the Convection Electric Field into the Inner Magnetosphere and the Resulting Plasma Injection.- 5.6. Geomagnetic and Magnetospheric Storms.- References.- 6 Magnetotail Phenomena During Magnetospheric Substorms.- 6.1. Introduction.- 6.2. B Vector Dipping.- 6.3. Plasma Sheet Thinning.- 6.3.1. Profile of Thinning.- (a) Z-axis Dependence.- (b) Profile in the Y-Z Plane.- (c) Profile in the X-Y Plane.- (d) Profile in the X-Z Plane.- 6.3.2. Timing of Thinning.- 6.3.3. Thinning and the Bz Component Reversal.- 6.3.4. Summary.- 6.4. Magnetotail Field BT and Radius RT.- 6.4.1. Decrease of the Magnetotail Lobe Field BT.- 6.4.2. Decrease of the Radius of the Magnetotail RT.- 6.5. Auroral Bulge.- 6.5.1. Auroral Bulge.- 6.5.2. Auroral Particles in the Bulge.- 6.5.3. Increase of the Magnetic Field Component Bz.- 6.5.4. Increase of Cosmic Ray Proton Cut-off.- 6…