dorsal/arxiv
View SchemaShell to shell energy transfer in MHD, Part II: Kinematic dynamo
| Authors | Pablo D. Mininni, Alexandros Alexakis, Annick Pouquet |
|---|---|
| Categories | |
| ArXiv ID | physics/0505189 |
| URL | https://arxiv.org/abs/physics/0505189 |
| DOI | 10.1103/PhysRevE.72.046302 |
Abstract
We study the transfer of energy between different scales for forced three-dimensional MHD turbulent flows in the kinematic dynamo regime. Two different forces are examined: a non-helical Taylor Green flow with magnetic Prandtl number P_M=0.4, and a helical ABC flow with P_M=1. This analysis allows us to examine which scales of the velocity flow are responsible for dynamo action, and identify which scales of the magnetic field receive energy directly from the velocity field and which scales receive magnetic energy through the cascade of the magnetic field from large to small scales. Our results show that the turbulent velocity fluctuations are responsible for the magnetic field amplification in the small scales (small scale dynamo) while the large scale field is amplified mostly due to the large scale flow. A direct cascade of the magnetic field energy from large to small scales is also present and is a complementary mechanism for the increase of the magnetic field in the small scales. Input of energy from the velocity field in the small magnetic scales dominates over the energy that is cascaded down from the large scales until the large-scale peak of the magnetic energy spectrum is reached. At even smaller scales, most of the magnetic energy input is from the cascading process.
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"abstract": "We study the transfer of energy between different scales for forced\nthree-dimensional MHD turbulent flows in the kinematic dynamo regime. Two\ndifferent forces are examined: a non-helical Taylor Green flow with magnetic\nPrandtl number P_M=0.4, and a helical ABC flow with P_M=1. This analysis allows\nus to examine which scales of the velocity flow are responsible for dynamo\naction, and identify which scales of the magnetic field receive energy directly\nfrom the velocity field and which scales receive magnetic energy through the\ncascade of the magnetic field from large to small scales. Our results show that\nthe turbulent velocity fluctuations are responsible for the magnetic field\namplification in the small scales (small scale dynamo) while the large scale\nfield is amplified mostly due to the large scale flow. A direct cascade of the\nmagnetic field energy from large to small scales is also present and is a\ncomplementary mechanism for the increase of the magnetic field in the small\nscales. Input of energy from the velocity field in the small magnetic scales\ndominates over the energy that is cascaded down from the large scales until the\nlarge-scale peak of the magnetic energy spectrum is reached. At even smaller\nscales, most of the magnetic energy input is from the cascading process.",
"arxiv_id": "physics/0505189",
"authors": [
"Pablo D. Mininni",
"Alexandros Alexakis",
"Annick Pouquet"
],
"categories": [
"physics.flu-dyn",
"physics.plasm-ph"
],
"doi": "10.1103/PhysRevE.72.046302",
"title": "Shell to shell energy transfer in MHD, Part II: Kinematic dynamo",
"url": "https://arxiv.org/abs/physics/0505189"
},
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