It is typically assumed that the kinetic and magnetic helicities play a crucial role in the growth of large-scale dynamo. In this paper, we demonstrate that helicity is not essential for the amplification of large-scale magnetic field. For this purpose, we perform nonhelical magnetohydrodynamic (MHD) simulation, and show that the large-scale magnetic field can grow in nonhelical MHD when random external forcing is employed at scale 1/10 the box size. The energy fluxes and shell-to-shell transfer rates computed using the numerical data show that the large-scale magnetic energy grows due to the energy transfers from the velocity field at the forcing scales.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We are grateful to the anonymous referee for comments that helped us improve the manuscript. We thank Amitava Bhattacharjee and Rodion Stepanov for the suggestions and comments, and Abhishek Kumar for his help with performing some simulations. The computer simulations were performed on Shaheen II of the Supercomputing Laboratory at King Abdullah University of Science and Technology (KAUST) under the project K1052, and on Chaos supercomputer of Simulation and Modeling Laboratory (SML), IIT Kanpur. This work was supported by the Indo-French research project SERB/F/3279/2013-14 from Science and Engineering Research Board, India and by the Indo-Russian project (DST-RSF) INT/RUS/RSF/P-03 and RSF-16-41-02012.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.