TITLE

Beta-induced Alfvén-acoustic eigenmodes in stellarator plasmas with low shear

AUTHOR(S)
Eremin, D. Yu.; Könies, A.
PUB. DATE
January 2010
SOURCE
Physics of Plasmas;Jan2010, Vol. 17 Issue 1, p012108
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The coupling of low-frequency Alfvénic modes with acoustic oscillations due to curvature of the background magnetic field is considered for stellarator plasmas with low shear. Magnetohydrodynamic (MHD) analysis demonstrates that the interaction between these branches can generate gaps in the continua with a width proportional to beta as well as the magnitude of the Fourier harmonics of the magnetic field strength which cause the coupling. The gaps can provide a habitat for beta-induced Alfvén-acoustic eigenmodes (BAAEs). Using the causality principle, a technique is developed to resolve the singular behavior of the MHD BAAE eigenmode equation at the points of resonance with the acoustic continuum. Alternatively, the singularities arising in the reduced MHD description can be resolved by accounting for the finite parallel electrical field. Both approaches yield consistent continuum damping rate, which proves to be small. Numerical calculations for analytically fitted experimental profiles of electron-dominated plasma in Helically Symmetric eXperiment (HSX) facility yield two weakly damped BAAE modes with different frequencies: one is close to the maximum of the lower-frequency Alfvén-acoustic continuum, and the other is located well within the BAAE gap. The numerically found BAAEs have frequencies in the same range as the experimentally observed electromagnetic modes in HSX, even when the finite diamagnetic frequency effects are considered.
ACCESSION #
47807082

 

Related Articles

  • A matching problem revisited for stability analysis of resistive wall modes in flowing plasmas. Shiraishi, J.; Tokuda, S.; Aiba, N. // Physics of Plasmas;Jan2010, Vol. 17 Issue 1, p012504 

    The classical matching problem for magnetohydrodynamic stability analysis is revisited to study effects of the plasma flow on the resistive wall modes (RWMs). The Newcomb equation, which describes the marginal states and governs the regions except for the resonant surface, is generalized to...

  • A method for finding three-dimensional magnetic skeletons. Haynes, A. L.; Parnell, C. E. // Physics of Plasmas;Sep2010, Vol. 17 Issue 9, p092903 

    Magnetic fields are an essential component of a plasma. In many astrophysical, solar, magnetospheric, and laboratory situations the magnetic field in the plasma can be very dynamic and form highly complex structures. One approach to unraveling these structures is to determine the magnetic...

  • Modeling the Parker instability in a rotating plasma screw pinch. Khalzov, I. V.; Brown, B. P.; Katz, N.; Forest, C. B. // Physics of Plasmas;Feb2012, Vol. 19 Issue 2, p022107 

    We analytically and numerically study the analogue of the Parker (magnetic buoyancy) instability in a uniformly rotating plasma screw pinch confined in a cylinder. Uniform plasma rotation is imposed to create a centrifugal acceleration, which mimics the gravity required for the classical Parker...

  • Stationary nontearing inertial scale electron magnetohydrodynamic instability. Lukin, V. S. // Physics of Plasmas;Dec2009, Vol. 16 Issue 12, p122105 

    Two-dimensional stationary nontearing inertial scale electron magnetohydrodynamic (EMHD) instability is described. The physical mechanism of the instability is illustrated. Analytical asymptotic estimate of the growth rate is provided and verified with a numerical calculation of the instability,...

  • Self-organization in three-dimensional compressible magnetohydrodynamic flow. Horiuchi, Ritoku; Sato, Tetsuya // Physics of Fluids (00319171);May88, Vol. 31 Issue 5, p1142 

    A three-dimensional self-organization process of a compressible dissipative plasma with a velocity-magnetic field correlation is investigated in detail by means of a variational method and a magnetohydrodynamic simulation. There are two types of relaxation, i.e., fast relaxation in which the...

  • Qualitative Models of the Enhanced-Rate Propagation of a Magnetic Field in a Plasma due to the Hall Effect. Kukushkin, A. B.; Cherepanov, K. V. // Plasma Physics Reports;May2000, Vol. 26 Issue 5, p428 

    Two qualitative electron magnetohydrodynamic models are developed of an enhanced-rate (in comparison with ordinary diffusion) propagation of a magnetic field in a plasma due to the Hall effect. The first model is based on a simple hydrodynamic approach, which in particular makes it possible to...

  • Magnetohydrodynamics of a Weakly Ionized Plasma: Ambipolar Magnetic Diffusion and Shock Front Structure. Sokolov, I. V.; Sakai, J. I. // Plasma Physics Reports;Jun2000, Vol. 26 Issue 6, p493 

    Kinetic equations with the BGK collision integral are used to derive MHD equations for a weakly ionized plasma that are applicable over a broad range of magnetic field strengths. In strong magnetic fields, a substantial contribution to the transverse diffusion of the magnetic field comes from...

  • Three-Dimensional MHD Simulations of Forced Magnetic Reconnection. Bulanov, S. V.; Echkina, E. Yu.; Inovenkov, I. N.; Pegoraro, F.; Pichushkin, V. V. // Plasma Physics Reports;Apr2001, Vol. 27 Issue 4, p315 

    Results are presented from MHD simulations of three-dimensional flows of a high-conductivity plasma in the vicinity of a null point of a magnetic field. The excitation of an electric current at the boundary of the computation region results in self-consistent plasma flows and change in the...

  • On the dynamics of a plasma vortex street and its topological signatures. Siregar, E.; Stribling, W.T.; Goldstein, M.L. // Physics of Plasmas;Jul94, Vol. 1 Issue 7, p2125 

    Focuses on the interaction between two- and three-dimensional plasma modes and a mean sheared magnetic field using a three-dimensional magnetohydrodynamic spectral Galerkin computation. Possible evolution of a plasma vortex street configuration when two velocity and one magnetic shear layer...

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics