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Five-minute oscillations on the Sun (acoustic and surface gravity waves) areexcited by subsurface turbulent convection. However, in sunspots the excitationis suppressed because strong magnetic field inhibits convection. We use 3Dsimulations to investigate how the suppression of excitation sources affectsthe distribution of the oscillation power in sunspot regions. The amplitude ofrandom acoustic sources was reduced in circular-shaped regions to simulate thesuppression in sunspots. The simulation results show that the amplitude of theoscillations can be approximately 2-4 times lower in the sunspot regions incomparison to the quiet Sun, just because of the suppressed sources. UsingSOHO/MDI data we measured the amplitude ratio for the same frequency bandsoutside and inside sunspots, and found that this ratio is approximately 3-4.Hence, the absence of excitation sources inside sunspots makes a significantcontribution (about 50% or higher) to the observed amplitude ratio and must betaken into account in sunspot seismology.

Effect of suppressed excitation on the amplitude distribution of 5-min oscillations in sunspots