If our eyes were radio rather than optical wide-band detectors it is well known that for us the brightest object in the sky would still be the Sun; that planets, stars and the Milky Way would still shine feebly (and that we would still occasionally be blinded by man-made sources). What is less well known is that quite a different earthbound overcast would hover about us, with its climatic zones, its seasonal changes, its unpredictable storms and scintillating transparence. To be sure, we can get a sort of glimpse of this peculiar type of weather when we tune our receiver to radio broad­ casting from some remote spot, or photograph the Earth from space at certain specific wavelengths. Nevertheless no one has ever looked at the ionized shroud of the Earth without the help of sophisticated apparatus, and this is one of the reasons why in this domain the phenomena are not easily abstracted from the use of specific techniques. For generations, the study of the ionosphere has been deeply interwoven with the practice of radio communication and detection. Today however, ionospheric physics is best thought of as a branch of space physics; that part of physics which deals with processes at work in the solar system and methods developed for its exploration.

Inhalt

One/The Ionospheric Environment.- I / The Atmosphere and the Vertical Structure of the Ionospheric Plasma.- 1.1. Hydrostatic Equilibrium in the Earth's Gravitational Field.- 1.2. The Interaction Between the Ultraviolet Solar Spectrum and the Atmosphere.- 1.3. Stratifications of the Ionosphere.- II / The Latitudinal Structure of the Ionosphere and the Magnetosphere.- 2.1. Terrestrial Magnetism.- 2.2. The Interaction between the Solar Wind and the Geomagnetic Field.- 2.3. The Dynamics of Charged Particles.- 2.4. Magnetospheric Activity and Substorms.- Two/The Techniques of Ionospheric Measurements.- III / Propagation of Radio Waves.- 3.1. Electromagnetic Waves in Plasmas.- 3.2. The Reflection of Radio Waves by the Ionosphere.- 3.3. Phase Effects with High Frequency Waves.- 3.4. Group Effects with Lower Frequency Waves.- 3.5. The Effects of Collisions.- IV / Scattering of Radio Waves.- 4.1. Quasi-Specular Reflexion from Ionospheric Irregularities.- 4.2. Scattering from VolumeTlasma Fluctuations.- 4.3. Implementation of Incoherent Scatter Sounding.- V / Sampling With Space-Borne Probes.- 5.1. The Langmuir Characteristic.- 5.2. Specific Problems Connected with Space Vehicles.- 5.1. Plasma Probes.- 5.2. Electrostatic Analyzers.- 5.3. Mass Spectrometers.- Three/The Interpretation of Ionospheric Phenomena.- VI / Chemistry of Charge Conservation.- 6.1. Ion Chemical Processes.- 6.2. The Chemical Structure of the Ionosphere.- 6.3. Photoionization.- 6.4. Corpuscular Ionization.- 6.5. Meteor Ionization.- VII / Electrodynamics of Momentum Transfer.- 7.1. The Bulk Motions of Ions and Electrons.- 7.2. Ionospheric Electric Fields and Currents.- 7.3. The Distribution of Hydrogen Ions and the Upper Ionosphere.- 7.4. The Behaviour of Atomic Oxygen Ions and the F layer.- 7.5. The Formation of Sporadic E layers at Temperate Latitudes.- VIII / Thermodynamics of Energy Balance.- 8.1. Energy Budget of the Charged Particles.- 8.2. Electron and Ion Temperatures in the Mid and Low Latitude Regions.- 8.3. Geomagnetic Control of Ionospheric Temperature.- References.