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Wave Damping by Magnetohydrodynamic Turbulence and Its Effect on Cosmic-Ray Propagation in the Interstellar Medium

Farmer, Alison J. and Goldreich, Peter (2004) Wave Damping by Magnetohydrodynamic Turbulence and Its Effect on Cosmic-Ray Propagation in the Interstellar Medium. Astrophysical Journal, 604 (2). pp. 671-674. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20130225-091451386

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Abstract

Cosmic rays scatter off magnetic irregularities (Alfvén waves) with which they are resonant, that is, waves of wavelength comparable to their gyroradii. These waves may be generated either by the cosmic rays themselves, if they stream faster than the Alfvén speed, or by sources of MHD turbulence. Waves excited by streaming cosmic rays are ideally shaped for scattering, whereas the scattering efficiency of MHD turbulence is severely diminished by its anisotropy. We show that MHD turbulence has an indirect effect on cosmic-ray propagation by acting as a damping mechanism for cosmic-ray-generated waves. The hot ("coronal") phase of the interstellar medium is the best candidate location for cosmic-ray confinement by scattering from self-generated waves. We relate the streaming velocity of cosmic rays to the rate of turbulent dissipation in this medium for the case in which turbulent damping is the dominant damping mechanism. We conclude that cosmic rays with up to 10^2 GeV could not stream much faster than the Alfvén speed but 10^6 GeV cosmic rays would stream unimpeded by self-generated waves, unless the coronal gas were remarkably turbulence-free.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1086/382040 DOIUNSPECIFIED
http://iopscience.iop.org/0004-637X/604/2/671/PublisherUNSPECIFIED
http://lanl.arxiv.org/abs/astro-ph/0311400v1arXivUNSPECIFIED
Alternate Title:Wave damping by MHD turbulence and its effect upon cosmic ray propagation in the ISM
Additional Information:© 2004 The American Astronomical Society. Received 2003 November 16; accepted 2003 December 15. This research was supported in part by NSF grant AST 00- 98301. The authors thank Russell Kulsrud for raising the issue discussed in this paper and for illuminating discussions.
Funders:
Funding AgencyGrant Number
NSFAST 00-98301
Subject Keywords:cosmic rays — MHD — turbulence
Issue or Number:2
Record Number:CaltechAUTHORS:20130225-091451386
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130225-091451386
Official Citation:Wave Damping by Magnetohydrodynamic Turbulence and Its Effect on Cosmic-Ray Propagation in the Interstellar Medium Alison J. Farmer and Peter Goldreich 2004 ApJ 604 671
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37105
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Feb 2013 21:22
Last Modified:03 Oct 2019 04:44

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