Analysis of the Hermite spectrum in plasma turbulence
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Univ. of Texas at Austin, Austin, TX (United States)
The properties of the Hermite spectrum associated with the linear drift-kinetic equation—as used in studies of gyrokinetic turbulence—are examined. A rigorous uniform asymptotic expression is derived for the steady-state spectrum with a Lenard-Bernstein collision operator. It is found that the spectrum is partitioned into three regions whose boundaries are determined by the ratio of the collision frequency ν to the parallel transit frequency kvth. In the regime of small Hermite index, n, with n ≲ (ν/kvth)2/3, collisions play no role, and the free energy decays like n–1/2 due to phase mixing. In the previously unexplored large-n regime, n ≥ (ν/kvth)2, collisions are dominant, and the decay of the free energy spectrum is extremely steep, falling off like (n/e)–n. Most of the free energy is dissipated in the intermediate regime, (ν/kvth)2/3 ≲ n << (ν/kvth)2, where the asymptotic spectrum is in close agreement with the exponentially decaying “continuization” estimate. Furthermore, our analysis shows that collisions act as a singular perturbation, giving rise to the intermediate regime, where collisions are significantly altering the spectrum well inside the general large-n asymptotic region.
- Research Organization:
- Univ. of Texas, Austin, TX (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- FG02-04ER54742
- OSTI ID:
- 1523377
- Alternate ID(s):
- OSTI ID: 1400334
- Journal Information:
- Physics of Plasmas, Vol. 24, Issue 10; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Symmetries of a reduced fluid-gyrokinetic system
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journal | March 2018 |
Laboratory space physics: Investigating the physics of space plasmas in the laboratory
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journal | May 2018 |
An integral transform technique for kinetic systems with collisions
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journal | August 2018 |
Laboratory Space Physics: Investigating the Physics of Space Plasmas in the Laboratory | text | January 2018 |
An integral transform technique for kinetic systems with collisions | text | January 2018 |
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