This Encyclopedia aims, basically, at summanzmg the wealth of well­ established facts and outlining the relevant theories in the different branches of physics. With this as goal, the writers were asked to present their specific field in such a way that access is possible to any scientist without special a priori information in that field; the basic concepts of physics are assumed to be known to the reader. The survey given in each paper was also to be long­ lasting, so that even a few years after publication, each volume would be useful, for example as an introduction for newcomers or as a source of information for workers in a neighbouring field. In the field of geophysics, dealt with in Vols. 47--49 of the Encyclopedia, this task is difficult to achieve because during the last decades there has been a much faster development of basic information and theory than during the decades before. When I came to contribute to this work the famous Julius Bartels, then editor of the geophysical part, told me that Vol. 49 should certainly take into account the results of the "International Geophysical Year" 1957/58 (I. G. Y. ), and that we had better wait until these were accessible than produce a kind of information which might be obsolete in a short time.

Inhalt

Modelling of the Solar Extreme Ultraviolet Irradiance for Aeronomic Applications..- I. Temporal variations of the solar irradiance.- 1. Introduction.- 2. Solar EUV measurements aeronomic interest.- II. Representation and estimation of solar EUV fluxes.- 3. Representation of solar EUV fluxes.- 4. Estimation of the solar EUV fluxes from ground-based measurements.- 5. EUV fluxes as solar indices.- III. Aeronomical implications of the solar EUV radiation.- 6. Computation of ionospheric parameters.- 7. Atmospheric heating by solar EUV radiation.- Transport Coefficients and Collision Frequencies for Aeronomic Plasmas..- A. Transport coefficients derived with a mean-collision-frequency method.- 1. Momentum and energy flux balance.- 2. Transport equations.- B. Gas kinetic cross sections and collision frequencies.- 3. General methods of the kinetic theory.- I. Transfer cross sections and transfer collision frequencies.- 4. Collision cross sections and collision frequencies.- 5. Quantum corrections to classical transfer cross sections.- 6. Transfer cross sections.- 7. Transfer cross sections for nonmonotonic interaction potentials.- 8. Transfer cross sections for monotonic interactions potentials.- II. Transfer cross sections for particular interactions.- 9. Collisions between charged and neutral particles.- 10. Collisions between electrons and neutral particles. General features.- 11. Collisions between electrons and aeronomic neutrals.- 12. Collisions between charged particles.- 13. Collisions between ions and neutrals. Polarization part.- 14. Collisions between atomic ions and atoms.- 15. Collisions of ions in their parent gas. Charge exchange.- 16. Collisions of ions on their parent gas. Polarization.- 17. Collisions between neutrals.- 18. Analytic expressions and normalizations for transfer cross sections and transfer collision frequencies.- III. Transport collision frequencies and their calculation.- 19. Transport collision frequencies.- 20. Transport collision frequencies for multiparameter interaction potentials.- 21. Numerical and analytical results for transport collision frequencies.- 22. Survey of the methods for the determination of transport collision frequencies.- C. The moment method.- I. System of balance equations for momentum and heat flux.- 23. Momentum and heat flux balances.- 24. Balance equations in matrix notation.- II. Transport equations.- 25. Transport equations in zeroth approximation. Ohm's and Fourier's laws.- 26. Transport equations in first approximation. Thermal diffusion and diffusion thermo effect.- 27. Onsager-Casimir relations. Generalized Bridgman relation.- III. Particular transport coefficients.- 28. Transport coefficients for charged particles and for electrons alone.- 29. Electrical and heat conductivity for an electron plasma.- 30. Thermal diffusion tensor and Peltier tensor for an electron plasma.- D. The Lorentz method.- 31. Representation of transport coefficients.- 32. Eigenvalues of the transport tensors expressed by Dingle integrals.- 33. Binomial approximations of the transport eigenvalues.- 34. The Ginzburg-Gurevic representation of transport eigenvalues.- 35. The Shkarofsky representation of transport eigenvalues.- 36. Some applications and extensions.- Append.- A. Axial tensors and axial matrix tensors.- B. Some definite integrals and special functions.- C. Conversion of units.- General references.- Modelling of Neutral and Ionized Atmospheres..- 1. Fundamental relations.- A. Measurements.- 2. Air density determinations from satellite drag.- 3. In-situ composition measurements.- 4. Other measurements of neutral atmosphere parameters.- 5. Incoherent scatter sounding.- 6. Optical methods of observation.- B. Results.- 7. Temperature in the upper atmosphere.- 8. Atmospheric structure and transport.- 9. Composition.- C. Empirical (descriptive) modeling.- 10. International reference atmospheres.- 11. Computerized descriptive models of the neutral atmosphere.- 12. Intercomparison of different atmospheric models.- D. Empirical modelling of the ionosphere.- 13. Modelling vertical profiles.- 14. Worldwide aspect of the ionosphere.- E. Aeronomical modeling.- 15. Kinematic models.- 16. Thermospheric heat budget.- 17. Advanced aeronomical theory.- 18. The polar caps: coupling with the magnetosphere.- Appendix A: The Role of Photoelectrons in the Heat Balance of the Upper Atmosphere.- General references.- Errata to Volumes XLIX/3-6.