Magnetic dynamo action in helical turbulence

Abstract

We investigate magnetic field amplification in a turbulent velocity field with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan model. We present the numerical solution of the model for the practically important case of Kolmogorov distribution of velocity fluctuations, with a large magnetic Reynolds number. We find that in contrast to the nonhelical case where growing magnetic fields are described by a few bound eigenmodes concentrated inside the inertial interval of the velocity field, in the helical case the number of bound eigenmodes considerably increases; moreover, new unbound eigenmodes appear. Both bound and unbound eigenmodes contribute to the large-scale magnetic field. This indicates a limited applicability of the conventional alpha model of a large-scale dynamo action, which captures only unbound modes.

10 pages, 1 figure (with minor changes to match published version)

References in corpus (3)

• On magnetic field generation in Kolmogorov turbulence
• Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers
• Magnetic-field generation in helical turbulence

Cited by in corpus (10)

• Dynamo theories
• A new interpretation of the far-infrared - radio correlation and the expected breakdown at high redshift
• The small-scale dynamo: Breaking universality at high Mach numbers
• Effects of helical magnetic fields on the cosmic microwave background
• Traces of large-scale dynamo action in the kinematic stage
• Magnetic dynamo action at low magnetic Prandtl numbers
• Magnetic dynamo action in random flows with zero and finite correlation times
• Non-Gaussian generalization of the Kazantsev-Kraichnan model
• Magnetic dynamo action in astrophysical turbulence
• Amplification of magnetic fields by dynamo action in Gaussian-correlated helical turbulence