The Role of Helical and Non-Helical Drives on the evolution of Self-Consistent Dynamos

Abstract

In the self-consistent dynamo limit, the magnetic feedback on the velocity field is sufficiently strong to induce a change in the topology of the magnetic field. Consequently, the magnetic energy reaches a state of non-linear saturation. Here, we investigate the role played by helical and non-helical drives in the triggering and the eventual saturation of a self-consistent dynamo. Evidence of small-scale dynamo (SSD) activity is found for both helical and non-helical forcing, driven at the largest possible scale. Based on the spectrum analysis, we find that the evolution of kinetic energy follows Kolmogorov's $k^-{\frac{5}{3}}$ law while that of magnetic energy follows Kazantsev's $k^{\frac{3}{2}}$ scaling. Also, we have verified that the aforementioned scalings remain valid for various magnetic Prandtl numbers (Pm). Statistical analysis is found to support our numerical finds.