Contamination by Surface Effects of Time-distance Helioseismic Inversions for Sound Speed Beneath Sunspots

Abstract

Using Doppler velocity data from the SOI/MDI instrument onboard the SoHO spacecraft, we do time-distance helioseismic inversions for sound-speed perturbations beneath 16 sunspots observed in high-resolution mode. We clearly detect ring-like regions of enhanced sound speed beneath most sunspot penumbrae, extending from near the surface to depths of about 3.5 Mm. Due to their location and dependence on frequency bands of p-modes used, we believe these rings to be artifacts produced by a surface signal probably associated with the sunspot magnetic field.

accepted by ApJ

References in corpus (3)

• Surface Magnetism Effects in Time-Distance Helioseismology
• Sensitivity of time-distance helioseismic measurements to spatial variation of oscillation amplitudes I. Observations and a numerical model
• Radiative transfer effects on Doppler measurements as sources of surface effects in sunspot seismology

Cited by in corpus (16)

• Helioseismology of Sunspots: A Case Study of NOAA Region 9787
• Surface-focused Seismic Holography of Sunspots: I. Observations
• Theoretical modeling of propagation of magneto-acoustic waves in magnetic regions below sunspots
• Numerical Models of Travel-Time Inhomogeneities in Sunspots
• Time-Distance Modelling In A Simulated Sunspot Atmosphere
• Magnetic and Thermal Phase Shifts in the Local Helioseismology of Sunspots
• Newly identified properties of surface acoustic power
• Physical Properties of Wave Motion in Inclined Magnetic Fields Within Sunspot Penumbrae
• Flows around Averaged Solar Active Regions
• Helioseismic Holography of Simulated Sunspots: dependence of the travel time on magnetic field strength and Wilson depression
• Directional Time-Distance Probing of Model Sunspot Atmospheres
• Helioseismic holography of simulated sunspots: magnetic and thermal contributions to travel times
• Helioseismic Travel-Time Definitions and Sensitivity to Horizontal Flows Obtained From Simulations of Solar Convection
• A Study of Acoustic Halos in Active Region NOAA 11330 using Multi-Height SDO Observations
• A statistical study of the subsurface structure and eruptivity of solar active regions
• Deep-Focus Diagnostics of Sunspot Structure