Magnetohydrodynamic (MHD) waves - last update: 13 June 1996, 0740 UT (RR)
Magnetohydrodynamic (MHD) plasma theory deals with a compressible, conducting fluid immersed in a magnetic field. The wave modes derived using this theory are called magnetohydrodynamic or MHD waves. In the general case, with the wave propagation in an arbitrary direction with respect to external magnetic field B, three MHD wave modes are found: (There will be a figure here showing how the different wave modes are related.) These relate with the three different oblique shock types in ideal MHD.

All these waves have constant phase velocities for all frequencies, and hence there is no dispersion. At the limits when the angle a between the wave propagation vector k and magnetic field B is either 0 (180) or 90 degrees, the very same wave modes are called as:

When the fluid is not perfectly conducting, but has a finite conductivity, or if viscous effects are present, the MHD oscillations will be damped.

See also: