Transport of Protostellar Cosmic Rays in Turbulent Dense Cores

Abstract

Recent studies have suggested that low-energy cosmic rays (CRs) may be accelerated inside molecular clouds by the shocks associated with star formation. We use a Monte Carlo transport code to model the propagation of CRs accelerated by protostellar accretion shocks through protostellar cores. We calculate the CR attenuation and energy losses and compute the resulting flux and ionization rate as a function of both radial distance from the protostar and angular position. We show that protostellar cores have non-uniform CR fluxes that produce a broad range of CR ionization rates, with the maximum value being up to two orders of magnitude higher then the radial average at a given distance. In particular, the CR flux is focused in the direction of the outflow cavity, creating a 'flashlight' effect and allowing CRs to leak out of the core. The radially averaged ionization rates are less than the measured value for the Milky Way of $\zeta \approx 10^{-16}{\mathrm{s}}^{-1}$; however, within $r\approx 0.03$ pc from the protostar, the maximum ionization rates exceed this value. We show that variation in the protostellar parameters, particularly in the accretion rate, may produce ionization rates that are a couple of orders of magnitude higher or lower than our fiducial values. Finally, we use a statistical method to model unresolved sub-grid magnetic turbulence in the core. We show that turbulence modifies the CR spectrum and increases the uniformity of the CR distribution but does not significantly affect the resulting ionization rates.

References in corpus (34)

• Theory of Star Formation
• The Magnetic Fields of Classical T Tauri Stars
• Magnetic Fields in the Formation of Sun-Like Stars
• The Effects of Radiative Transfer on Low-Mass Star Formation
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core
• Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
• A SCUBA survey of Orion, the low-mass end of the core mass function
• The importance of the ortho:para H2 ratio for the deuteration of molecules during pre-protostellar collapse
• Survey of ortho-H2D+(1_{1,0}-1_{1,1}) in dense cloud cores
• The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars
• Effective destruction of CO by cosmic rays: implications for tracing H${}_2$ gas in the Universe
• The origin of galactic cosmic rays
• SPIRou: the near-infrared spectropolarimeter/high-precision velocimeter for the Canada-France-Hawaii telescope
• Complex organics in IRAS 4A revisited with ALMA and PdBI: Striking contrast between two neighbouring protostellar cores
• Impact of Protostellar Outflows on Turbulence and Star Formation Efficiency in Magnetized Dense Cores
• Modelling [CI] emission from turbulent molecular clouds
• SOLIS II. Carbon-chain growth in the Solar-type protocluster OMC2-FIR4
• The Green Bank Ammonia Survey: Dense Cores Under Pressure in Orion A
• Impulsive Spot Heating and Thermal Explosion of Interstellar Grains Revisited
• Cosmic ray penetration in diffuse clouds
• Magnetohydrodynamic-Particle-in-Cell Simulations of the Cosmic-Ray Streaming Instability: Linear Growth and Quasi-linear Evolution
• The Highly Collimated Radio Jet of HH 80-81: Structure and Non-Thermal Emission
• Tentative Evidence for Relativistic Electrons Generated by the Jet of the Young Sun-like Star DG Tau
• The Astrochemical Impact of Cosmic Rays in Protoclusters I: Molecular Cloud Chemistry
• Diffusive Versus Free-Streaming Cosmic Ray Transport in Molecular Clouds
• Synthetic Observations of Magnetic Fields in Protostellar Cores
• Protostellar Outflows at the EarliesT Stages (POETS). II. A possible radio synchrotron jet associated with the EGO G035.02+0.35
• The ionising effect of low energy cosmic rays from a class II object on its protoplanetary disk
• Evidence for a Cosmic Ray Gradient in the IM Lup Protoplanetary Disk
• Neutral vs Ion Linewidths in Barnard 5: Evidence for Penetration by MHD Waves
• Aluminum-26 Enrichment in the Surface of Protostellar Disks Due to Protostellar Cosmic Rays
• Effects of Turbulence on Cosmic Ray Propagation in Protostars and Young Star/Disk Systems
• Cosmic Ray transport in mixed magnetic fields and their role on the observed anisotropies

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• The impact of cosmic-ray attenuation on the carbon cycle emission in molecular clouds
• Gas phase Elemental abundances in Molecular cloudS (GEMS) V. Methanol in Taurus
• The cosmic ray ionisation and $\gamma$-ray budgets of star-forming galaxies
• A 3D physico-chemical model of a pre-stellar core. I. Environmental and structural impact on the distribution of CH${}_3$OH and $c$-C${}_3$H${}_2$
• Stellar Energetic Particle Transport in the Turbulent and CME-disrupted Stellar Wind of AU~Microscopii
• Interstellar Glycolaldehyde, Methyl Formate, and Acetic Acid. II. Chemical Modeling of the Bimodal Abundance Pattern in NGC 6334I
• Modeling Hadronic Gamma-ray Emissions from Solar Flares and Prospects for Detecting Non-thermal Signatures from Protostars
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