Evidence for solar frequency dependence on sunspot type
  High degree solar mode frequencies as measured by ring diagrams are known to change in the presence of the strong magnetic fields found in active regions. We examine these changes in frequency for a large sample of active regions analyzed with data from the Michelson Doppler Imager (MDI) onboard the SoHO spacecraft, spanning most of solar cycle 23. We confirm that the frequencies increase with increasing magnetic field strength, and that this dependence is generally linear. We find that the dependence is slightly but significantly different for active regions with different sunspot types. 
Charles S. Baldner, Richard S. Bogart, and Sarbani Basu
astro-ph.SR