| longitudinal magnetohydrodynamic wave
Note 1 to entry: The movement of the particles of the fluid is parallel to the direction of propagation of the magnetosonic wave; its wave vector k is orthogonal to the magnetic flux density.
The phase velocity of magnetosonic waves is
is the sound wave velocity (in a gas, )
is the Alfvén wave velocity
is the speed of light in vacuum
Note 2 to entry: For low magnetic fields, the phase velocity of the magnetosonic wave approaches sound wave velocity.