scale of the system. For example, could be the minor radius of the torus in a tokamak.

Relativistic case

The Alfvén wave velocity in relativistic magnetohydrodynamics is

where is the total energy density of plasma particles, is the total plasma pressure, and

is the magnetic pressure. In the non-relativistic limit, where , this formula reduces to the one given previously.

Alfvén wave modes

Alfvén waves can propagate