Verma, Mahendra K. ; Kumar, Rohit (2016) Dynamos at extreme magnetic Prandtl numbers: insights from shell models Journal of Turbulence, 17 (12). pp. 1112-1141. ISSN 1468-5248
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Official URL: http://doi.org/10.1080/14685248.2016.1228937
Related URL: http://dx.doi.org/10.1080/14685248.2016.1228937
Abstract
We present an MHD shell model suitable for computation of various energy fluxes of magnetohydrodynamic turbulence for very small and very large magnetic Prandtl numbers Pm; such computations are inaccessible to direct numerical simulations. For small Pm, we observe that both kinetic and magnetic energy spectra scale as k−5/3 in the inertial range, but the dissipative magnetic energy scales as k−11/3exp(−k/kη). Here, the kinetic energy at large length scale feeds the large-scale magnetic field that cascades to small-scale magnetic field, which gets dissipated by Joule heating. The large-Pm dynamo has a similar behaviour except that the dissipative kinetic energy scales as k−13/3. For this case, the large-scale velocity field transfers energy to the large-scale magnetic field, which gets transferred to small-scale velocity and magnetic fields; the energy of the small-scale magnetic field also gets transferred to the small-scale velocity field, and the energy thus accumulated is dissipated by the viscous force.
Item Type: | Article |
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Source: | Copyright of this article belongs to Taylor and Francis Ltd. |
ID Code: | 118936 |
Deposited On: | 04 Jun 2021 12:29 |
Last Modified: | 04 Jun 2021 12:29 |
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