The authors postulate nothing but the Maxwell equations. They discuss at length the disk dynamo, which serves as a model for the natural self-excited dynamos that generate magnetic fields such as that of sunspots.

There are 36 Examples and 13 Case Studies. The Case Studies concern solar phenomena -- magnetic elements, sunspots, spicules, coronal loops -- and the Earth's magnetic field.

Auteur

Paul Lorrain is the main author of three books: Electromagnetic Fields and Waves, third edition 1988, Electromagnetism, Principles and Applications, second edition, 1990, and Fundamentals of Electromagnetic Phenomena, first edition 2000, all published by Freeman, New York. He is also the main author of 22 papers published in the last 22 years in major physics, astrophysics, and plasma physics journals. He has worked in universities and research institutes in several countries. He is presently Visiting Professor in the Department of Earth and Planetary Sciences at McGill University in Montréal, Canada.

François Lorrain is a co-author of the first and third of the above three books. He has also published a book, Réseaux sociaux et classifications sociales ; essai sur l'algèbre et la géométrie des structures sociales, Hermann, Paris, 1975. In relation to Magneto-Fluid-Dynamics, he has recently published an article entitled "Estimating the order of magnitude of derivatives in physics by means of characteristic lengths and times" in the American Journal of Physics, 72 (5), May 2004, pp. 683-690. Presently he teaches in the Département de mathématiques et d'informatique, Collège Jean-de-Brébeuf, Montréal (QC), Canada.

Résumé
Magnetohydrodynamics (MHD) concerns the interaction between magnetic fields and conducting fluids. We are concerned here with macroscopic inter actions and, when the conducting fluid is a plasma, time scales are very much longer than the plasma period. Plasma periods vary widely, but are short, say 10~^^ second. We prefer the term Magneto-F/i^Z(i-Dynamics (MFD) because the disci pline concerns mostly plasmas, various liquid conductors, and the liquid part of the Earth's core. It seems that the only applications of MFD to water are the induction of electric currents in the oceans by the Earth's magnetic field, and ship propulsion. But even MFD is not quite appropriate because that term also includes solid conductors that move in magnetic fields. This book is meant for graduate and upper-division undergraduate stu dents in Physics, Geophysics, and Astrophysics, as well as for practicing sci entists in these fields. This book is no more than a brief introduction to MFD because this vast subject is closely related to many others, namely Astrophysics, Elec trodynamics, Fluid Dynamics, Geophysics, Oceanography, Plasma Physics, Thermonuclear Fusion, etc. We sketch the fundamentals, and provide many Examples, as well as Case Studies related to natural phenomena. MFD sorely needs a rethink: it must of course be totally compatible with Physics. On the contrary, it is the custom to discuss the shapes of imaginary magnetic field lines, without ever referring to the required electric currents.

Contenu
The Early History.- The Early History.- Fundamentals.- The Maxwell Equations.- Electric Fields.- Constant Magnetic Fields.- Time-dependent Magnetic Fields: The Law of Faraday.- Moving Conductors.- Ohm's Law for Moving Conductors.- Charges Inside Moving Conductors.- Nine Examples: Magnetic Fields in Moving Conductors.- Case Study: The Azimuthal Magnetic Field in the Earth's Core.- Natural Dynamos.- Case Study: The Disk Dynamo Model for Natural Dynamos.- Three Case Studies: Magnetic Flux Tubes, Flux Ropes, and Flux Coils.- Case Study: Solar Magnetic Elements.- Case Study: Sunspots.- Case Study: Solar Spicules.- Case Study: Solar Coronal Loops as Self-Channeled Proton Beams I.- Case Study: Solar Coronal Loops as Self-Channeled Proton Beams II.- Appendices.- Characteristic Lengths and Times, a Justification1.- SI prefixes.