An Etymological Dictionary of Astronomy and Astrophysics

The speed at which → Alfven waves are propagated along the magnetic field. It is a characteristic velocity at which perturbations of the lines of force travel. Alfvén speed is given by: v_A = B/(μ₀.ρ)^1/2, where B is the → magnetic field strength, μ₀ is the → magnetic permeability, and ρ is the density of the plasma. Alfvén speed plays a role analogous to the sound speed in non-magnetized fluid dynamics. Same as Alfvén velocity.

See also: → Alfvén wave; → speed.