Cosmic-Ray Propagation: Nonlinear Diffusion Parallel and Perpendicular to Mean Magnetic Field

By Huirong Yan, A. Lazarian. 2007

191 citations recorded by the source corpus.

We consider the propagation of cosmic rays in turbulent magnetic fields. We use the models of magnetohydrodynamic turbulence that were tested in numerical simulations, in which the turbulence is injected on large scales and cascades to small scales. Our attention is focused on the models of the strong turbulence, but we also briefly discuss the effects that the weak turbulence and the slab Alfvénic perturbations can have. The latter are likely to emerge as a result of instabilities within the cosmic-ray fluid itself, e.g., beaming and gyroresonance instabilities of cosmic rays. To describe the interaction of cosmic rays with magnetic perturbations we develop a nonlinear formalism that extends the ordinary quasi-linear theory that is routinely used for the purpose. This allows us to avoid the usual problem of 90° scattering and enables our computation of the mean free path of cosmic rays. We apply the formalism to the cosmic-ray propagation in the Galactic halo and in the warm ionized medium. In addition, we address the issue of the transport of cosmic rays perpendicular to the mean magnetic field and show that the issue of cosmic-ray subdiffusion (i.e., propagation with retracing the trajectories backward, which slows down the diffusion) is only important for restricted cases when the ambient turbulence is far from what numerical simulations suggest to us. As a result, this work provides formalism that can be applied for calculating cosmic-ray propagation in a wide variety of circumstances.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5db15f81635d5988bd660801ded40945ae17e84b

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Citations in the corpus

A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays - II. Results for the diffusion model combining B/C and radioactive nuclei (2010, background): “…predictions for the transport in turbulent magnetic fields (e.g., Casse et al. 2002; Ptuskin et al. 2006; Minnie et al. 2007; Tautz et al. 2008, Yan & Lazarian 2008 and references therein), or related to the source spectra predicted in acceleration models (e.g., Marcowith et al. 2006; Uchiyama…”
The Nine Lives of Cosmic Rays in Galaxies (2015, background): “• The possibly strong environmental effects on the diffusion properties via the level of interstellar MHD turbulence and, in particular, of fast magnetosonic modes that efficiently scatter CRs (Yan & Lazarian 2008).”
Galactic winds driven by cosmic ray streaming (2012, background): “Consequently, a number of authors have worked on the problem of CR streaming in high-beta plasmas (Holman, Ionson & Scott 1979; Achterberg 1981; Felice & Kulsrud 2001; Yan & Lazarian 2008), and a summary of these works can be found in Enßlin et al. (2011).”
MAXIMALLY STAR-FORMING GALACTIC DISKS. I. STARBURST REGULATION VIA FEEDBACK-DRIVEN TURBULENCE (2011, unknown): “The mean free path of cosmic rays, Lcr, is likely comparable the magnetic scale height LB (Yan & Lazarian 2008).”
Cosmic ray transport in galaxy clusters: implications for radio halos, gamma-ray signatures, and cool core heating (2010, background): “Possible processes can help in crossing the μcr = 0 gap, include mirroring on long wavelength waves (Achterberg 1981; Felice & Kulsrud 2001), and resonance broadening which relaxes the resonant condition (Achterberg 1981; Yan & Lazarian 2008).”