Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence
A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g., drift-wave turbulence driven by temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating ExB flows and of...
| Main Authors: | , , , , , |
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| 格式: | Journal article |
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Cambridge University Press
2016
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| _version_ | 1826259228083355648 |
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| author | Schekochihin, A Parker, J Highcock, E Dellar, P Dorland, W Hammett, G |
| author_facet | Schekochihin, A Parker, J Highcock, E Dellar, P Dorland, W Hammett, G |
| author_sort | Schekochihin, A |
| collection | OXFORD |
| description | A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g., drift-wave turbulence driven by temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating ExB flows and of its phase mixing, which is caused by the streaming of the particles along the mean magnetic field and, in a linear problem, would lead to Landau damping. A consistent theory is constructed in which very little free energy leaks into high velocity moments of the distribution, rendering the turbulent cascade in the energetically relevant part of the wave-number space essentially fluid-like. The velocity-space spectra of free energy expressed in terms of Hermite-moment orders are steep power laws and so the free-energy content of the phase space does not diverge at infinitesimal collisionality (while it does for a linear problem); collisional heating due to long-wavelength perturbations vanishes in this limit (also in contrast with the linear problem, in which it occurs at the finite rate equal to the Landau-damping rate). The ability of the free energy to stay in the low velocity moments of the distribution is facilitated by the "anti-phase-mixing" effect, whose presence in the nonlinear system is due to the stochastic version of the plasma echo (the advecting velocity couples the phase-mixing and anti-phase-mixing perturbations). The partitioning of the wave-number space between the (energetically dominant) region where this is the case and the region where linear phase mixing wins is governed by the "critical balance" between linear and nonlinear timescales (which for high Hermite moments splits into two thresholds, one demarcating the wave-number region where phase mixing predominates, the other where plasma echo does). |
| first_indexed | 2024-03-06T18:46:33Z |
| format | Journal article |
| id | oxford-uuid:0eb884d9-8a7e-4e97-b1c7-0e80f0e7983b |
| institution | University of Oxford |
| last_indexed | 2024-03-06T18:46:33Z |
| publishDate | 2016 |
| publisher | Cambridge University Press |
| record_format | dspace |
| spelling | oxford-uuid:0eb884d9-8a7e-4e97-b1c7-0e80f0e7983b2022-03-26T09:47:27ZPhase mixing vs. nonlinear advection in drift-kinetic plasma turbulenceJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:0eb884d9-8a7e-4e97-b1c7-0e80f0e7983bSymplectic Elements at OxfordCambridge University Press2016Schekochihin, AParker, JHighcock, EDellar, PDorland, WHammett, GA scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g., drift-wave turbulence driven by temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating ExB flows and of its phase mixing, which is caused by the streaming of the particles along the mean magnetic field and, in a linear problem, would lead to Landau damping. A consistent theory is constructed in which very little free energy leaks into high velocity moments of the distribution, rendering the turbulent cascade in the energetically relevant part of the wave-number space essentially fluid-like. The velocity-space spectra of free energy expressed in terms of Hermite-moment orders are steep power laws and so the free-energy content of the phase space does not diverge at infinitesimal collisionality (while it does for a linear problem); collisional heating due to long-wavelength perturbations vanishes in this limit (also in contrast with the linear problem, in which it occurs at the finite rate equal to the Landau-damping rate). The ability of the free energy to stay in the low velocity moments of the distribution is facilitated by the "anti-phase-mixing" effect, whose presence in the nonlinear system is due to the stochastic version of the plasma echo (the advecting velocity couples the phase-mixing and anti-phase-mixing perturbations). The partitioning of the wave-number space between the (energetically dominant) region where this is the case and the region where linear phase mixing wins is governed by the "critical balance" between linear and nonlinear timescales (which for high Hermite moments splits into two thresholds, one demarcating the wave-number region where phase mixing predominates, the other where plasma echo does). |
| spellingShingle | Schekochihin, A Parker, J Highcock, E Dellar, P Dorland, W Hammett, G Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence |
| title | Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence |
| title_full | Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence |
| title_fullStr | Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence |
| title_full_unstemmed | Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence |
| title_short | Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence |
| title_sort | phase mixing vs nonlinear advection in drift kinetic plasma turbulence |
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