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Meromorphy and topology of localized solutions in the Thomas–MHD model

Published online by Cambridge University Press:  01 February 2002

J.-D. FOURNIER
Affiliation:
Department G.D. Cassini, Observatoire de la Côte d'Azur and CNRS, BP 4229, 06304 Nice Cedex 4, France
S. GALTIER
Affiliation:
Department G.D. Cassini, Observatoire de la Côte d'Azur and CNRS, BP 4229, 06304 Nice Cedex 4, France Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK Present and permanent address: Institut d'Astrophysique Spatiale, Université Paris XI, 91405 Orsay Cedex, France

Abstract

The one-dimensional MHD system first introduced by J.H. Thomas [Phys. Fluids 11, 1245 (1968)] as a model of the dynamo effect is thoroughly studied in the limit of large magnetic Prandtl number. The focus is on two types of localized solutions involving shocks (antishocks) and hollow (bump) waves. Numerical simulations suggest phenomenological rules concerning their generation, stability and basin of attraction. Their topology, amplitude and thickness are compared favourably with those of the meromorphic travelling waves, which are obtained exactly, and respectively those of asymptotic descriptions involving rational or degenerate elliptic functions. The meromorphy bars the existence of certain configurations, while others are explained by assuming imaginary residues. These explanations are tested using the numerical amplitude and phase of the Fourier transforms as probes of the analyticity properties. Theoretically, the proof of the partial integrability backs up the role ascribed to meromorphy. Practically, predictions are derived for MHD plasmas.

Type
Research Article
Copyright
2001 Cambridge University Press

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