Helio- and Asteroseismology


Nodal points

An oscillation on the surface of the Sun or a distant star has a characteristic pattern of nodal points, where there isn't any motion, distributed over the solar or stellar disc You can think, for example, of a skipping rope, which is fixed at one end, while the other end is moved up and down vigorously. If you move your hand with an appropriate speed, you can create a so-called standing wave, where the nodal points are the places on the rope that are standing still, while the rest of the rope moves up and down. On a two-dimensional surface, such as a drumskin or the solar surface, the nodal points are arranged in nodal lines; in a three-dimensional object, for instance the solar interior, the nodal points form nodal surfaces.