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Toward a theory of interstellar turbulence. 2: Strong alfvenic turbulenceWe continue to investigate the possibility that interstellar turbulence is caused by nonlinear interactions among shear Alfven waves. Here, we restrict attention to the symmetric case where the oppositely directed waves carry equal energy fluxes. This precludes application to the solar wind in which the outward flux significantly exceeds the ingoing one. All our detailed calculations are carried out for an incompressible magnetized fluid. In incompressible magnetohydrodynamics (MHD), nonlinear interactions only occur between oppositely direct waves. We present a theory for the strong turbulence of shear Alfven waves. It has the following main characteristics. (1) The inertial-stage energy spectrum exhibits a critical balance between linear wave periods and nonlinear turnover timescales. (2) The 'eddies' are elongated in the direction of the field on small spatial scales; the parallel and perpendicular components of the wave vector, k(sub z) and k(perpendicular) are related by k(sub z) approximately equals k(sub perpendicular to)(exp 2/3) L(exp -1/3), where L is the outer scale of the turbulence. (3) The 'one-dimensional' energy spectrum is proportional to k(sub perpendicular)(exp -5/3)-an anisotropic Kolmogorov energy spectrum. Shear Alfvenic turbulence mixes specific entropy as a passive contaminant. This gives rise to an electron density power spectrum whose form mimics the energy spectrum of the turbulence. Radio wave scattering by these electron density fluctuations produces anisotropic scatter-broadened images. Damping by ion-neutral collisions restricts Alfvenic turbulence to highly ionized regions of the interstellar medium.
Document ID
19950036979
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Goldreich, P.
(California Institute of Technology, Pasadena, CA United States)
Sridhar, S.
(Univ. of Toronto Toronto, Canada)
Date Acquired
August 16, 2013
Publication Date
January 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 438
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A68578
Funding Number(s)
CONTRACT_GRANT: NAGW-2372
CONTRACT_GRANT: NSF 89-13664
Distribution Limits
Public
Copyright
Other

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