Amplification and saturation of turbulent magnetic field in collapsing primordial gas clouds

Abstract

Recent numerical studies suggest that magnetic fields play an important role in primordial star formation in the early universe. However, the detailed evolution of the magnetic field in the collapse phase still has uncertainties because of the complicated physics associated with turbulence in a collapsing magnetized system. Here, we perform a suite of numerical MHD simulations that follow the collapse of magnetized, turbulent primordial gas clouds to investigate the evolution of the magnetic field associated with the turbulence, assuming a polytropic equation of state with exponent ${\gamma }_{\mathrm{eff}}$ and with various numerical resolutions. In addition, we generalize the analytic theory of magnetic field growth/saturation so that it can deal with various exponents ${\gamma }_{\mathrm{eff}}$ and turbulence energy spectra. We find that the numerical results are well reproduced by the theory for various ${\gamma }_{\mathrm{eff}}$ through the collapse phase during the formation of the first stars. The magnetic field is eventually amplified by a factor of $10^{12}$ -- $10^{15}$ due to kinematic and non-linear turbulent dynamo effects and reaches 3% -- 100% of the equipartition level, depending on ${\gamma }_{\mathrm{eff}}$. We also find that the transition between the kinematic and non-linear stages can be analytically estimated. These results indicate that the strong magnetic field accompanied by supersonic turbulence is a general property and suggest that it can play a crucial role in the formation of the first stars.

15 pages, 8 figures, 1 tables, accepted for publication in ApJ

References in corpus (31)

• The Athena++ Adaptive Mesh Refinement Framework: Design and Magnetohydrodynamic Solvers
• The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
• Protostar Formation in the Early Universe
• Simulations of nonhelical hydromagnetic turbulence
• The Mass Spectrum of the First Stars
• A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence
• The First Galaxies: Assembly, Cooling and the Onset of Turbulence
• Suppression of H_2 Cooling in the Ultraviolet Background
• Magnetic field amplification in turbulent astrophysical plasmas
• The sonic scale revealed by the world's largest supersonic turbulence simulation
• The Turbulent Dynamo in Highly Compressible Supersonic Plasmas
• Formation sites of Population III star formation: The effects of different levels of rotation and turbulence on the fragmentation behavior of primordial gas
• Merge or survive: Number of Population III stars per minihalo
• Turbulent dynamo in a conducting fluid and partially ionized gas
• Magnetic Fields in the Formation of the First Stars. I. Theory vs. Simulation
• Seed magnetic fields in turbulent small-scale dynamos
• Magnetic fields in the formation of the first stars.--II Results
• Efficient highly-subsonic turbulent dynamo and growth of primordial magnetic fields
• Fundamental scales in the kinematic phase of the turbulent dynamo
• Formation of Massive and Wide First-star Binaries in Radiation Hydrodynamics Simulations
• Molecular cloud formation by compression of magnetized turbulent gas subjected to radiative cooling
• The Athena++ Adaptive Mesh Refinement Framework: Multigrid Solvers for Self-Gravity
• Dissipation of magnetic fields in star-forming clouds with different metallicities
• Nonlinear turbulent dynamo during gravitational collapse
• Magnetohydrodynamic effect on first star formation: prestellar core collapse and protostar formation
• Amplification of turbulence in contracting prestellar cores in primordial minihalos
• Exponentially amplified magnetic field eliminates disk fragmentation around the Population III protostar
• Ionization degree and magnetic diffusivity in the primordial star-forming clouds
• Non-ideal magnetohydrodynamic simulations of the first star formation: the effect of ambipolar diffusion
• Saturation level of turbulence in collapsing gas clouds
• Merger Conditions of Population III Protostar Binaries

Cited by in corpus (2)

• Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics
• Population III star formation in the presence of turbulence, magnetic fields and ionizing radiation feedback