Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers.
Direct numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic Reynolds number Rm>>1 and small magnetic Prandtl number Pm<<1. The depende...
| Main Authors: | , , , , |
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| Format: | Journal article |
| Language: | English |
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2007
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| _version_ | 1826276102396444672 |
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| author | Iskakov, AB Schekochihin, A Cowley, S McWilliams, J Proctor, MR |
| author_facet | Iskakov, AB Schekochihin, A Cowley, S McWilliams, J Proctor, MR |
| author_sort | Iskakov, AB |
| collection | OXFORD |
| description | Direct numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic Reynolds number Rm>>1 and small magnetic Prandtl number Pm<<1. The dependence of the critical Rmc for dynamo on the hydrodynamic Reynolds number Re is obtained for 1 less than or similar Re less than or similar 6700. In the limit Pm<<1, Rmc is about 3 times larger than for the previously well-established dynamo at large and moderate Prandtl numbers: Rmc less than or similar 200 for Re greater than or similar 6000 compared to Rmc approximately 60 for Pm>or=1. It is not yet possible to determine numerically whether the growth rate of the magnetic energy is proportional, Rm1/2 in the limit Rm-->infinity, as it should be if the dynamo is driven by the inertial-range motions at the resistive scale. |
| first_indexed | 2024-03-06T23:08:56Z |
| format | Journal article |
| id | oxford-uuid:64ce0a91-8b69-4a7a-8319-35b339f1cc52 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:08:56Z |
| publishDate | 2007 |
| record_format | dspace |
| spelling | oxford-uuid:64ce0a91-8b69-4a7a-8319-35b339f1cc522022-03-26T18:21:14ZNumerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:64ce0a91-8b69-4a7a-8319-35b339f1cc52EnglishSymplectic Elements at Oxford2007Iskakov, ABSchekochihin, ACowley, SMcWilliams, JProctor, MRDirect numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic Reynolds number Rm>>1 and small magnetic Prandtl number Pm<<1. The dependence of the critical Rmc for dynamo on the hydrodynamic Reynolds number Re is obtained for 1 less than or similar Re less than or similar 6700. In the limit Pm<<1, Rmc is about 3 times larger than for the previously well-established dynamo at large and moderate Prandtl numbers: Rmc less than or similar 200 for Re greater than or similar 6000 compared to Rmc approximately 60 for Pm>or=1. It is not yet possible to determine numerically whether the growth rate of the magnetic energy is proportional, Rm1/2 in the limit Rm-->infinity, as it should be if the dynamo is driven by the inertial-range motions at the resistive scale. |
| spellingShingle | Iskakov, AB Schekochihin, A Cowley, S McWilliams, J Proctor, MR Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers. |
| title | Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers. |
| title_full | Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers. |
| title_fullStr | Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers. |
| title_full_unstemmed | Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers. |
| title_short | Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers. |
| title_sort | numerical demonstration of fluctuation dynamo at low magnetic prandtl numbers |
| work_keys_str_mv | AT iskakovab numericaldemonstrationoffluctuationdynamoatlowmagneticprandtlnumbers AT schekochihina numericaldemonstrationoffluctuationdynamoatlowmagneticprandtlnumbers AT cowleys numericaldemonstrationoffluctuationdynamoatlowmagneticprandtlnumbers AT mcwilliamsj numericaldemonstrationoffluctuationdynamoatlowmagneticprandtlnumbers AT proctormr numericaldemonstrationoffluctuationdynamoatlowmagneticprandtlnumbers |