Efficiency of magnetic dynamo action at low magnetic Prandtl numbers

Amplification of magnetic field due to kinematic turbulent dynamo action is studied in the regime of small magnetic Prandtl numbers. An analysis based on the Kazantsev-Kraichnan model is used to establish the dynamo threshold and the dynamo growth rates for varying kinetic helicity of turbulent fluctuations. It is found that in contrast with the case of large magnetic Prandtl numbers, the kinematic dynamo action at small magnetic Prandtl numbers is significantly affected by kinetic helicity, and it can be made quite efficient with an appropriate choice of the helicity spectrum.