Ideal ballooning stability near an equilibrium magnetic island

Technical Report · Sun Mar 01 04:00:00 EST 1992

DOI:https://doi.org/10.2172/10137308· OSTI ID:10137308

Hegna, C C; Callen, J D

The stability properties of ideal ballooning modes on toroidal flux surfaces near a quasistatic magnetic island is examined. On these surfaces, magnetic field-line trajectories tend to bunch on that part of the magnetic surface closet to the X-point of the magnetic island. Because of this preferential bunching, the stabilizing effect of field-line bending due to magnetic shear can be reduced. Eigenfunctions localized in helical angle near the X-point and in poloidal angle on the bad curvature side of the tokamak are more susceptible to ballooning instability than are modes in corresponding equilibria without the magnetic island. For a slowly growing island, a growing number of flux surfaces located near the separatrix become ballooning unstable. Secondary ballooning instabilities may play a part in the crash phase of sawteeth or macroscopic island dynamics.

• Research Organization: Wisconsin Univ., Madison, WI (United States). Center for Plasma Theory and Computation
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-86ER53218
• OSTI ID: 10137308
• Report Number(s): UW-CPTC--92-1; ON: DE92011730
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700340
BALLOONING INSTABILITY
MAGNETIC FIELDS
MAGNETIC ISLANDS
MHD EQUILIBRIUM
PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES
TOKAMAK DEVICES
TRAJECTORIES