Dynamos

Dynamos is a collection of lectures given in July 2007 at the Les Houches Summer School on "Dynamos". Provides a pedagogical introduction to topics in Dynamos Addresses each topic from the basis to the most recent developments Covers the lectures by internationally-renowned and leading experts

Comprised of lectures for an intensive course held at the Newton Institute in Cambridge, as part of a NATO Advanced Study Institute, the topics covered within this volume include planetary and solar dynamos, fast dynamos, and the use of symmetry principles to derive evolution equations.

Nonlinear dynamo theory is central to understanding the magnetic structures of planets, stars and galaxies. In chapters contributed by some of the leading scientists in the field, this text explores some of the recent advances in the field. Both kinetic and dynamic approaches to the subject are considered, including fast dynamos, topological methods in dynamo theory, physics of the solar cycle and the fundamentals of mean field dynamo. Advances in Nonlinear Dynamos is ideal for graduate students and researchers in theoretical astrophysics and applied mathematics, particularly those interested in cosmic magnetism and related topics, such as turbulence, convection, and more general nonlinear physics.

Although the origin of Earth's and other celestial bodies' magnetic fields remains unknown, we do know that the motion of electrically conducting fluids generates and maintains these fields, forming the basis of magnetohydrodynamics (MHD) and, to a larger extent, dynamo theory. Answering the need for a comprehensive, interdisciplinary introduction to this area, Mathematical Aspects of Natural Dynamos provides a foundation in dynamo theory before moving on to modeling aspects of natural dynamos. Bringing together eminent international contributors, the book first introduces governing equations, outlines the kinematic dynamo theory, covers nonlinear effects, including amplitude saturation and polarity reversals, and discusses fluid dynamics. After establishing this base, the book describes the Earth's magnetic field and the current understanding of its characteristics. Subsequent chapters examine other planets in our solar system and the magnetic field of stars, including the sun. The book also addresses dynamo action on the large scale of galaxies, presents modeling experiments of natural dynamos, and speculates about future research directions. After reading this well-illustrated, thorough, and unified exploration, you will be well prepared to embark on your own journey through this fascinating area of research.

Astrophysical dynamos are at the heart of cosmic magnetic fields of a wide range of scales, from planets and stars to entire galaxies. This book presents a thorough, step-by-step introduction to solar and stellar dynamos. Looking first at the ultimate origin of cosmic seed magnetic fields, the antagonists of field amplification are next considered: resistive decay, flux expulsion, and flows ruled out by anti-dynamo theorems. Two kinematic flows that can act as dynamos are then studied: the Roberts cell and the CP-flow. Mean-field electrodynamics and derivation of the mean-field dynamo equations lead to the alpha Omega-dynamo, the flux transport dynamo, and dynamos based on the Babcock-Leighton mechanism. Alternatives to the mean-field theory are also presented, as are global MHD dynamo simulations. Fluctuations and grand minima in the solar cycle are discussed in terms of dynamo modulations through stochastic forcing and nonlinear effects. The book concludes with an overview of the major challenges in understanding stellar magnetic fields and their evolution in terms of various dynamo models, global MHD simulations, and fossil fields. Each chapter is accompanied by an annotated bibliography, guiding the readers to the relevant technical literature, which may lead them to carry out their own research in the field of dynamo theory.

Treats the origin of magnetic fields in planets, stars and galaxies, and the manner of their evolution over time.

The increasing power of computer resources along with great improvements in observational data in recent years have led to some remarkable and rapid advances in astrophysical fluid dynamics. The subject spans three distinct but overlapping communities whose interests focus on (1) accretion discs and high-energy astrophysics; (2) solar, stellar, and

Spheromaks are easily formed, self-organized magnetized plasma configurations that have intrigued plasma physicists for over two decades. Sometimes called magnetic vortices, magnetic smoke rings, or plasmoids, spheromaks first attracted attention as a possible controlled thermonuclear plasma confinement scheme, but are now known to have many other applications. This book begins with a review of the basic concepts of magnetohydrodynamics and toroidal magnetic configurations, then provides a detailed exposition of the 3D topological concepts underlying spheromak physics, namely magnetic helicity, Taylor relaxation, force-free equilibria, and tilt stability. It then examines spheromak formation techniques, driven and isolated configurations, dynamo concepts, practical experimental issues, diagnostics, and a number of applications. The book concludes by showing how spheromak ideas are closely related to the physics of solar prominences and interplanetary magnetic clouds. Contents: Basic ConceptsMagnetic HelicityRelaxation of an Isolated Configuration to the Taylor StateRelaxation in Driven ConfigurationsThe MHD Energy Principle, Helicity, and Taylor StatesSurvey of Spheromak Formation SchemesClassification of Regimes: An Imperfect Analogy to ThermodynamicsAnalysis of Isolated Cylindrical SpheromaksThe Role of the WallAnalysis of Driven Spheromaks: Strong CouplingHelicity Flow and DynamosConfinement and Transport in SpheromaksSome Important Practical IssuesBasic Diagnostics for SpheromaksApplications of SpheromaksSolar and Space Phenomena Related to Spheromaks Readership: Graduate students and advanced undergraduates who have taken a course in plasma magnetohydrodynamics, laboratory plasma physicists, solar & space plasma physicists, and scientists interested in the topological dynamics of self-organizing configurations. Keywords:Spheromak;Magnetohydrodynamics (MHD);Plasma;Self-Organization;Magnetic Helicity;Fusion;Solar;Coronal;Tokamak;Astrophysics;Relaxation;Taylor;Reversed Field Pinch (RFP);Dynamo