Alfvén wave

Summary

An Alfvén wave is a transverse wave of ideal MHD in which the fluid and the magnetic field oscillate together across a background field. Its restoring force is the tension of the magnetic field lines. It travels along the background field at the Alfvén speed $v_A = B_0 / \sqrt{\mu_0 \rho_0}$, whatever its wavelength, so it is not dispersive. Alfvén waves carry energy in the solar corona, the solar wind and fusion plasmas.