Evidence for solar frequency dependence on sunspot type

Abstract

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.

13 pages, 4 figures, accepted in ApJ letters

References in corpus (5)

• Helioseismology
• Ring diagram analysis of the characteristics of solar oscillation modes in active regions
• Surface Magnetism Effects in Time-Distance Helioseismology
• Physical Properties of Wave Motion in Inclined Magnetic Fields Within Sunspot Penumbrae
• Structure of the near-surface layers of the Sun: asphericity and time variation

Cited by in corpus (3)

• Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots
• Divergent Horizontal Sub-surface Flows within Active Region 11158
• The Sub-Surface Structure of a Large Sample of Active Regions