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Title: Analysis of the Hermite spectrum in plasma turbulence

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.5000518· OSTI ID:1523377

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
Citation Metrics:
Cited by: 4 works
Citation information provided by
Web of Science

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Cited By (5)

Symmetries of a reduced fluid-gyrokinetic system journal March 2018
Laboratory space physics: Investigating the physics of space plasmas in the laboratory journal May 2018
An integral transform technique for kinetic systems with collisions 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

Figures / Tables (1)


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