EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 437/1 Article
Free access article

Issue A&A
Volume 437, Number 1, July I 2005
Page(s) 1 - 8
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:20042433



A&A 437, 1-8 (2005)
DOI: 10.1051/0004-6361:20042433

Evolution of Alfvén waves by three-wave interactions in super-Alfvénic shocks

R. Vainio1 and F. Spanier2

1  Department of Physical Sciences, PO Box 64, 00014 University of Helsinki, Finland
    e-mail: rami.vainio@helsinki.fi
2  Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
    e-mail: fspanier@tp4.rub.de

(Received 25 November 2004 / Accepted 24 February 2005)

Abstract
We calculate the evolution of Alfvén waves in super-Alfvénic flows, such as the downstream region of a fast-mode shock, via three-wave interactions between two Aflvén waves and a sound wave. We show that the process has a significant influence on the evolution of the Alfvén wave spectra, driving the system toward a degenerate normalized cross-helicity, $H_{\rm c}\to\pm1$. Typical distances in which the system evolves are evaluated, and the effects of the calculated turbulence evolution on test-particle acceleration in super-Alfvénic quasi-parallel shocks are studied. We show that typically the spectrum of accelerated particles is determined by the first-order Fermi acceleration process as described earlier by Vainio & Schlickeiser (1998, A&A, 331, 793; 1999, A&A, 343, 303), and identify some regions of parameter space, where the earlier results are significantly modified either by changes in the predicted scattering-center compression ratio or by stochastic acceleration in the downstream plasma.


Key words: acceleration of particles -- magnetohydrodynamics (MHD) -- plasmas -- shock waves -- turbulence -- waves

SIMBAD Objects in preparation



© ESO 2005


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.