Magnetohydrodynamic Waves

Waves are extremely important and have been observed in a wide variety of solar phenomena. For example, observations have shown clear evidence for waves in sunspots, prominences, coronal fields and the overall oscillations of the Sun. The latter has led to the development of a new branch of solar physics called helioseismology whereby the surface oscillations are used to deduce the structure of the solar interior. The frequency of the oscillations provides useful information about the local plasma properties.

We might expect the MHD waves to be anisotropic because the magnetic field introduces a preferred direction to the plasma. To investigate the possible wave motions we assume that the amplitude of the waves is small so that we can linearise the MHD equations about a particular equilibrium.