In the previous chapter, we discussed the nature and properties of waves in a uniform medium. As mentioned earlier, by a uniform medium, we mean a medium wherein the physical variables such as velocity, density, pressure, and magnetic ﬁeld do not have discontinuities inside the medium. In this chapter, we shall extend the study of waves to nonuniform media , wherein we allow structures in the magnetic ﬁeld, discontinuities in density and pressure with ﬁnite geometries such as the slab and the cylinder. We will also study the behavior of waves in an annuli of cylinders, twisted magnetic ﬁelds. We shall brieﬂy discuss the propagation of nonlinear waves in a magnetically structured
medium. Evolution equations such as the KdV equation, Benjamin−Ono and Burger’s equations will also be dealt with brieﬂy.