The Magnetic Universe: Geophysical and Astrophysical Dynamo Theory

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WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2004. – 338 p. – ISBN: 3-527-40409-0.It is now 85 years since Sir Joseph Larmor first proposed that electromagnetic induction might be the origin of the Sun’s magnetic field (Larmor 1919). Today this so-called dynamo effect is believed to generate the magnetic fields of not only the Sun and other stars, but also the Earth and other planets, and even entire galaxies. Indeed, most of the objects in the Universe have associated magnetic fields, and most of these are believed to be due to dynamo action. Quite an impressive record for a paper that is only two pages long, and was written before galaxies other than the Milky Way were even known! However, despite this impressive list of objects to which Larmor’s idea has now been applied, in no case can we say that we fully understand all the details. Enormous progresshas undoubtedly been made, particularly with the huge increase in computational resources available in recent decades, but considerable progress remains to be made before we can say that we understand the magnetic fields even just of the Sun or the Earth, let alone some of the more exotic objects to which dynamo theory has been applied. Our goal in writing this book was therefore to present an overview of these various applications of dynamo theory, and in each case discuss what is known so far, but also what is still unknown. We specifically include both geophysical and astrophysical applications. There is an unfortunate tendency in the literature to regard stellar and planetary magnetic fields as somehow quite distinct. How this state of affairs came about is not clear, although it is most likely simply due to the fact that geophysics and astrophysics are traditionally separate departments. Regardless of its cause, it is certainly regrettable. We believe the two have enough in common that researchers in either field would benefit from a certain familiarity with the other area as well. ContentsIntroductionEarth and PlanetsDifferential Rotation TheoryThe Stellar DynamoThe Magnetorotational Instability (MRI)The Galactic Dynamo Neutron Star MagnetismThe Magnetic Taylor–Couette Flow