Small-scale dynamo with nonzero correlation time. Gopalakrishnan, K. & Singh, N. K. February, 2024. arXiv:2402.08366 [astro-ph, physics:physics]
Paper abstract bibtex The small-scale dynamo is typically studied by assuming that the correlation time of the velocity field is zero. Some authors have used a smooth renovating flow model to study how the properties of the dynamo are affected by the correlation time being nonzero. Here, we assume the velocity is an incompressible Gaussian random field (which need not be smooth), and derive the lowest-order corrections to the evolution equation for the two-point correlation of the magnetic field in Fourier space. Using this, we obtain the evolution equation for the longitudinal correlation function of the magnetic field in nonhelical turbulence, valid for arbitrary Prandtl number. Even at high Prandtl number, the derived evolution equation is qualitatively different from that obtained from the renovating flow model. Further, the growth rate of the magnetic energy is much smaller. Nevertheless, the magnetic power spectrum still retains the Kazantsev form at high Prandtl number.
@misc{gopalakrishnan_small-scale_2024,
title = {Small-scale dynamo with nonzero correlation time},
url = {http://arxiv.org/abs/2402.08366},
abstract = {The small-scale dynamo is typically studied by assuming that the correlation time of the velocity field is zero. Some authors have used a smooth renovating flow model to study how the properties of the dynamo are affected by the correlation time being nonzero. Here, we assume the velocity is an incompressible Gaussian random field (which need not be smooth), and derive the lowest-order corrections to the evolution equation for the two-point correlation of the magnetic field in Fourier space. Using this, we obtain the evolution equation for the longitudinal correlation function of the magnetic field in nonhelical turbulence, valid for arbitrary Prandtl number. Even at high Prandtl number, the derived evolution equation is qualitatively different from that obtained from the renovating flow model. Further, the growth rate of the magnetic energy is much smaller. Nevertheless, the magnetic power spectrum still retains the Kazantsev form at high Prandtl number.},
urldate = {2024-02-28},
publisher = {arXiv},
author = {Gopalakrishnan, Kishore and Singh, Nishant K.},
month = feb,
year = {2024},
note = {arXiv:2402.08366 [astro-ph, physics:physics]},
keywords = {astrophysics, magnetohydrodynamics, mentions sympy, perturbation methods},
}
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