Journal ArticleDOI
Interaction between hydromagnetic waves and a time-dependent, inhomogeneous medium.
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In this paper, the effect of the background on the wave and that of the wave on the background may be derived from Hamilton's principle using the averaged hydromagnetic Lagrangian density.Abstract:
Consider a system made up of a hydromagnetic wave and the slowly varying background fluid in which it propagates. It is shown that both the effect of the background on the wave and that of the wave on the background may be derived from Hamilton's principle using the averaged hydromagnetic Lagrangian density. The waves propagate adiabatically, conserving the wave action, and act on the background via a wave pressure term. Total momentum, angular momentum, and energy are conserved. When many waves are superimposed, as in weak turbulence, the wave kinetic equation replaces the adiabatic conservation equation. The accuracy of the averaging approximation is examined, and it is shown that it may be extended to all orders in the inhomogeneity. Also, Eulerian and Lagrangian averaging are discussed.read more
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Particle acceleration at astrophysical shocks: A theory of cosmic ray origin
TL;DR: In this article, the theory of first order Fermi acceleration at collisionless astrophysical shock fronts is reviewed and it is argued that the wave amplitude is probably non-linear within sufficiently strong astrophysical shocks.
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Control of star formation by supersonic turbulence
TL;DR: A review of the successes and problems of both the classical dynamical theory and the standard theory of magnetostatic support, from both observational and theoretical perspectives, is given in this paper.
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An introduction to the theory of diffusive shock acceleration of energetic particles in tenuous plasmas
TL;DR: In this article, the central idea of diffusive shock acceleration is presented from microscopic and macroscopic viewpoints; applied to reactionless test particles in a steady plane shock, the mechanism is shown to produce a power law spectrum in momentum with a slope which, to lowest order in the ratio of plasma to particle speed, depends only on the compression in the shock.
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The Formation of Massive Stars from Turbulent Cores
TL;DR: In this paper, the authors show that massive-star forming regions are supersonically turbulent, and that the molecular cores out of which individual massive stars form are as well, and they apply these results to predict the properties of protostars thought to be powering several observed hot molecular cores.
Control of Star Formation by Supersonic Turbulence
TL;DR: A review of the successes and problems of both the classical dynamical theory and the standard theory of magnetostatic support, from both observational and theoretical perspectives, is given in this article.
References
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Book
Electrodynamics of moving media
Paul Penfield,Hermann A. Haus +1 more
TL;DR: In this article, a nonrelativistic continuum mechanics and thermodynamics based approach is proposed for the nonlinearity of a simple polarizable fluid and the non-relativism of virtual power.