The frequencies of the global modes are shifted in the presence of surface magnetic acitivity. This image was generated by carrying out latitudinal 1-dimensional inversions of the frequency shifts within (n,l) multiplets for selected medium-degree modes, demonstrating the close temporal and spatial association of the shifts with the magnetic activity; the contours show a symmetrized version of the Kitt Peak synoptic magnetic data.

For more details, see Howe, R., Komm, R. W., & Hill, F. 2002, Astrophysical Journal 580, 1172 Localizing the Solar Cycle Frequency Shifts in Global p-Modes
This image uses data from GONG to give a continuous sequence of nearly 10 years' data.