Cosmic ray streaming in the turbulent interstellar medium

Abstract

We study the streaming instability of GeV$-100$GeV cosmic rays (CRs) and its damping in the turbulent interstellar medium (ISM). We find that the damping of streaming instability is dominated by ion-neutral collisional damping in weakly ionized molecular clouds, turbulent damping in the highly ionized warm medium, and nonlinear Landau damping in the Galactic halo. Only in the Galactic halo, is the streaming speed of CRs close to the Alfvén speed. Alfvénic turbulence plays an important role in both suppressing the streaming instability and regulating the diffusion of streaming CRs via magnetic field line tangling, with the effective mean free path of streaming CRs in the observer frame determined by the Alfvénic scale in super-Alfvénic turbulence. The resulting diffusion coefficient is sensitive to Alfvén Mach number, which has a large range of values in the multi-phase ISM. Super-Alfvénic turbulence contributes to additional confinement of streaming CRs, irrespective of the dominant damping mechanism.

11 pages, 4 figures, accepted for publication in ApJ

References in corpus (11)

• Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration
• Feedback Heating by Cosmic Rays in Clusters of Galaxies
• Spectral breaks as a signature of cosmic ray induced turbulence in the Galaxy
• Cosmic ray-driven galactic winds: streaming or diffusion?
• Cosmic ray transport in starburst galaxies
• Magnetic Field Morphology in Interstellar Clouds with the Velocity Gradient Technique
• Damping of Alfven waves by Turbulence and its Consequences: from Cosmic-Rays Streaming to Launching Winds
• Cosmic-Ray Diffusion Suppression in Star-forming Regions Inhibits Clump Formation in Gas-rich Galaxies
• Magnetic field amplification in supernova remnants
• On particle acceleration and transport in plasmas in the Galaxy: theory and observations
• Measuring magnetization with rotation measures and velocity centroids in supersonic MHD turbulence