From Glossary of Meteorology
(Also magnetohydrodynamic wave, hydromagnetic wave.) A transverse wave propagating along a magnetic field in an electrically conducting fluid (
This kind of wave does not exist in gases or fluids that are not ionized or in a plasma free from a magnetic field. The dynamics of such waves are analogous to those in a vibrating string.
Cowling, T. G. 1976. Magnetohydrodynamics. Ch. 3.