In every case the dotted circle shows where the turning point of the oscillation is. A frequency of 3 mHz is chosen in every case, which corresponds to an oscillation period of 5 min 20 sec. The different waves correspond to different values of the degree l (click on the small pictures to get animated sequences) :
Note that in the animations the waves move faster the deeper they penetrate into the Sun ; the reason for this is that the temperature, and therefore also the sound speed, increases as waves go deeper into the Sun. Note also that for l = 0 the waves actually go through the solar centre ; such waves correspond to purely radial oscillations in which the Sun expands and contracts but keeps its spherical shape.
Because the different waves penetrate to different depths, their frequencies are determined by conditions in different parts of the Sun. This can be used for inversion of the measured frequencies, to determine for instance how the speed of sound varies with depth in the Sun.