CRAFT (Cosmic Ray Acceleration From Turbulence) in Molecular Clouds

Abstract

Low-energy cosmic rays, in particular protons with energies below 1 GeV, are significant drivers of the thermochemistry of molecular clouds. However, these cosmic rays are also greatly impacted by energy losses and magnetic field transport effects in molecular gas. Explaining cosmic ray ionization rates of $10^{-16}$ s${}^{-1}$ or greater in dense gas requires either a high external cosmic ray flux, or local sources of MeV-GeV cosmic ray protons. We present a new local source of low-energy cosmic rays in molecular clouds: first order Fermi-acceleration of protons in regions undergoing turbulent reconnection in molecular clouds. We show from energetic-based arguments there is sufficient energy within the magneto-hydrodynamic turbulent cascade to produce ionization rates compatible with inferred ionization rates in molecular clouds. As turbulent reconnection is a volume-filling process, the proposed mechanism can produce a near-homogeneous distribution of low-energy cosmic rays within molecular clouds.

arXiv commentAccepted for publication by ApJL

References in corpus (33)

• Theory of Star Formation
• Reconnection in a Weakly Stochastic Field
• Cosmic-ray ionization of molecular clouds
• Investigating the Cosmic-Ray Ionization Rate in the Galactic Diffuse Interstellar Medium through Observations of H3+
• A PDR-Code Comparison Study
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• Cosmic Ray Scattering and Streaming in Compressible Magnetohydrodynamic Turbulence
• 3D Turbulent Reconnection: Theory, Tests and Astrophysical Implications
• Fast Magnetic Reconnection and Spontaneous Stochasticity
• The cosmic ray ionization rate in the Galactic disk, as determined from observations of molecular ions
• Protostars: Forges of cosmic rays?
• The Galactic Center Molecular Cloud Survey. I. A Steep Linewidth-Size Relation & Suppression of Star Formation
• Magnetohydrodynamic Simulations of Reconnection and Particle Acceleration: Three-Dimensional Effects
• Impact of low-energy cosmic rays on star formation
• Superdiffusion of Cosmic Rays: Implications for Cosmic Ray Acceleration
• AMS-02 beryllium data and its implication for cosmic ray transport
• Review of Zeeman Effect Observations of Regions of Star Formation
• Diffusion of cosmic rays in MHD turbulence with magnetic mirrors
• Penetration of cosmic rays into dense molecular clouds: role of diffuse envelope
• Exploration of Cosmic Ray Acceleration in Protostellar Accretion Shocks and A Model for Ionization Rates in Embedded Protoclusters
• Cosmic ray penetration in diffuse clouds
• SOLIS IV. Hydrocarbons in the OMC-2 FIR 4 region, a probe of energetic particle irradiation of the region
• What causes the ionization rates observed in molecular clouds? The role of cosmic ray protons and electrons
• Diffusive Versus Free-Streaming Cosmic Ray Transport in Molecular Clouds
• A magnetic reconnection model for explaining the multi-wavelength emission of the microquasars Cyg X-1 and Cyg X-3
• The physical and chemical structure of Sagittarius B2 -- V. Non-thermal emission in the envelope of Sgr B2
• Non-thermal emission from cosmic rays accelerated in HII regions
• Distributions of Short-Lived Radioactive Nuclei Produced by Young Embedded Stellar Clusters
• The diffuse gamma-ray emission toward the Galactic mini starburst W43
• Observational signatures of cosmic ray interactions in molecular clouds
• Spectrum of Relativistic and Subrelativistic Cosmic Rays in the 100 pc Central Region
• The onset of energetic particle irradiation in Class 0 protostars
• Intrusion of MeV-TeV Cosmic-Rays into Molecular Clouds Studied by Ionization, the Neutral Iron Line, and Gamma-Rays

Cited by in corpus (5)

• Cosmic rays in molecular clouds probed by H${}_2$ rovibrational lines -- Perspectives for the James Webb Space Telescope
• Low energy cosmic rays
• Stochasticity of Cosmic Rays from Supernova Remnants and the Ionization Rates in Molecular Clouds
• The cosmic ray ionisation and $\gamma$-ray budgets of star-forming galaxies
• Turbulent Reacceleration of Streaming Cosmic Rays