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

Abstract

Five-minute oscillations on the Sun (acoustic and surface gravity waves) are excited by subsurface turbulent convection. However, in sunspots the excitation is suppressed because strong magnetic field inhibits convection. We use 3D simulations to investigate how the suppression of excitation sources affects the distribution of the oscillation power in sunspot regions. The amplitude of random acoustic sources was reduced in circular-shaped regions to simulate the suppression in sunspots. The simulation results show that the amplitude of the oscillations can be approximately 2-4 times lower in the sunspot regions in comparison to the quiet Sun, just because of the suppressed sources. Using SOHO/MDI data we measured the amplitude ratio for the same frequency bands outside and inside sunspots, and found that this ratio is approximately 3-4. Hence, the absence of excitation sources inside sunspots makes a significant contribution (about 50% or higher) to the observed amplitude ratio and must be taken into account in sunspot seismology.

12 pages, 5 figures, accepted to ApJL

Cited by in corpus (5)

• Seismic Halos Around Active Regions: An MHD Theory
• MHS sunspot model from deep sub-photospheric to chromospheric layers
• Impact of Locally Suppressed Wave sources on helioseismic travel times
• Influence of Non-Uniform Distribution of Acoustic Wavefield Strength on Time-Distance Helioseismology Measurements
• Lifetimes of High-Degree p Modes in the Quiet and Active Sun