Macroscopic plasma oscillation bursts (fishbones) resulting from high-energy populations
Oscillation bursts (fishbones) of magnetically confined plasmas are associated with the excitation of an m/sup 0/ = 1 mode when the ideal magnetohydrodynamic (MHD) threshold for the instability of this mode is reached. Near this threshold and in the absence of an effective ''viscous'' dissipative process, this mode remains marginally stable as a result of finite ion Larmor radius effects and has a real frequency of oscillation near the ion diamagnetic frequency. The release of the mode excitation energy related to the gradient of the plasma pressure, in the case of perpendicular neutral beam injection, is allowed by the resonant interaction of the mode with fast trapped ions that precess around the torus as a result of the curvature and the gradient of the confining magnetic field. This process plays the role of an effective viscosity. A consequence of the presented interpretation is that fishbone oscillations may also be excited in the case of parallel beam injection. In fact, for relatively low values of the beam transverse pressure, the basic mode frequency is related to the parameters of the target plasma and does not depend on the magnetic drift frequency of the beam particles that are injected nor on their velocity distribution.
- Research Organization:
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- OSTI ID:
- 5153455
- Journal Information:
- Phys. Fluids; (United States), Vol. 31:6
- Country of Publication:
- United States
- Language:
- English
Similar Records
Alpha particle effects on the internal kink and fishbone modes
Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma
Related Subjects
PLASMA
FISHBONE INSTABILITY
EXCITATION
MAGNETOHYDRODYNAMICS
PLASMA MACROINSTABILITIES
THRESHOLD ENERGY
ENERGY
ENERGY-LEVEL TRANSITIONS
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MECHANICS
PLASMA INSTABILITY
700107* - Fusion Energy- Plasma Research- Instabilities