Magnetohydrodynamic waves in fusion and astrophysical plasmas.
Abstract
Macroscopic plasma dynamics in both controlled thermonuclear confinement machines and in the atmospheres of X-ray emitting stars is described by the equations of magnetohydrodynamics. This provides a vast area of overlapping research activities which is presently actively pursued. In this lecture the author concentrates on some important differences in the dynamics of the two confined plasma systems related to the very different geometries that are encountered and, thus, the role of the different boundary conditions that have to be posed. As a result, the basic MHD waves in a tokamak are quite different from those found in a solar magnetic flux tube. The result is that, whereas the three well-known MHD waves can be traced stepwise in the curved geometry of a tokamak, their separate existence is eliminated right from the start in a line-tied coronal loop because line-tying in general conflicts with the phase relationships between the vector components of the three velocity fields. The consequences are far-reaching, viz. completely different resonant frequencies and continuous spectra, absence of rational magnetic surfaces, and irrelevance of local marginal stability theory for coronal magnetic loops.
- Publication:
-
International Conference on Plasma Physics ICPP 1994
- Pub Date:
- 1995
- DOI:
- 10.1063/1.49008
- Bibcode:
- 1995AIPC..345..465G
- Keywords:
-
- Plasma: Astrophysics;
- Solar Magnetic Fields: Solar Coronal Loops;
- 52.35.Bj;
- 52.55.Fa;
- 98.70.Qy;
- Magnetohydrodynamic waves;
- Tokamaks spherical tokamaks;
- X-ray sources;
- X-ray bursts