The importance of anisotropic interstellar turbulence and molecular-cloud magnetic mirrors for galactic cosmic-ray propagation

Abstract

Recent studies suggest that when magnetohydrodynamic (MHD) turbulence is excited by stirring a plasma at large scales, the cascade of energy from large to small scales is anisotropic, in the sense that small-scale fluctuations satisfy the inequality k_parallel << k_perp, where k_parallel and k_perp are, respectively, the components of a fluctuation's wave vector parallel and perpendicular to the background magnetic field. Such anisotropic fluctuations are very inefficient at scattering cosmic rays. Results based on the quasilinear approximation for scattering of cosmic rays by anisotropic MHD turbulence are presented and explained. The important role played by molecular-cloud magnetic mirrors in confining and isotropizing cosmic rays when scattering is weak is also discussed.

5 pages, 5 figures. To appear in the Proceedings of the International Space Science Institute (ISSI) Conference on the Astrophysics of Galactic Cosmic Rays, Bern, Switzerland, 2000

References in corpus (2)

• The Anisotropy of MHD Alfvénic Turbulence
• Scattering of energetic particles by anisotropic magnetohydrodynamic turbulence with a Goldreich-Sridhar power spectrum

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