Negative-energy perturbations in circularly cylindrical equilibria within the framework of Maxwell-drift kinetic theory

Journal Article · Fri Mar 01 04:00:00 EST 1996 · Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

DOI:https://doi.org/10.1103/PhysRevE.53.2767· OSTI ID:282807

Throumoulopoulos, G N; Pfirsch, D ^[1]

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1. Division of Theoretical Physics, Department of Physics, University of Ioannina, P.O. Box 1186, GR 451 10 Ioannina (Greece)

The conditions for the existence of negative-energy perturbations (which could be nonlinearly unstable and cause anomalous transport) are investigated in the framework of linearized collisionless Maxwell-drift kinetic theory for the case of equilibria of magnetically confined, circularly cylindrical plasmas and vanishing initial field perturbations. For wave vectors with a nonvanishing component parallel to the magnetic field, the plane equilibrium conditions {l_brace}derived by Throumoulopoulos and Pfirsch {r_brace} are shown to remain valid, while the condition for perpendicular perturbations (which are found to be the most important modes) is modified. Consequently, besides the tokamak equilibrium regime in which the existence of negative-energy perturbations is related to the threshold value of 2/3 of the quantity {eta}{sub {nu}}={partial_derivative}ln{ital T}{sub {nu}}/{partial_derivative}ln{ital N}{sub {nu}}, a new regime appears, not present in plane equilibria, in which negative-energy perturbations exist for {ital any} value of {eta}{sub {nu}}. For various analytic cold-ion tokamak equilibria a substantial fraction of thermal electrons are associated with negative-energy perturbations (active particles). In particular, for linearly stable equilibria of a paramagnetic plasma with flat electron temperature profile ({eta}{sub {ital e}}=0), the entire velocity space is occupied by active electrons. The part of the velocity space occupied by active particles increases from the center to the plasma edge and is larger in a diamagnetic plasma than in a paramagnetic plasma with the same pressure profile. It is also shown that, unlike in plane equilibria, negative-energy perturbations exist in force-free reversed-field pinch equilibria with a substantial fraction of active particles. The fact that a threshold value of {eta}{sub {nu}} is not necessary for the existence of negative-energy perturbations, enhance even more the relevance of these modes.

• OSTI ID: 282807
• Journal Information: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Journal Name: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics Journal Issue: 3 Vol. 53; ISSN PLEEE8; ISSN 1063-651X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CYLINDRICAL CONFIGURATION
ELECTRON TEMPERATURE
KINETIC EQUATIONS
MAGNETIC CONFINEMENT
PLASMA DRIFT
PLASMA INSTABILITY
TOKAMAK DEVICES