Tomography of plasma flows in the upper solar convection zone using time--distance inversion combining ridge and phase-speed filtering

Abstract

The consistency of time--distance inversions for horizontal components of the plasma flow on supergranular scales in the upper solar convection zone is checked by comparing the results derived using two k--ωfiltering procedures -- ridge filtering and phase-speed filtering -- commonly used in time--distance helioseismology. It is shown that both approaches result in similar flow estimates when finite-frequency sensitivity kernels are used. It is further demonstrated that the performance of the inversion improves (in terms of simultaneously better averaging kernel and lower noise level) when the two approaches are combined together in one inversion. Using the combined inversion I invert for horizontal flows in the upper 10 Mm of the solar convection zone. The flows connected with supergranulation seem to be coherent only in the upper ~5 Mm depth, deeper down there is a hint on change of convection scales towards structures larger than supergranules.

25 pages manuscript, 10 figures, 4 tables, accepted for publication in ApJ

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• Issues with time--distance inversions for supergranular flows
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• Combined helioseismic inversions for 3D vector flows and sound-speed perturbations
• Plasma flows and sound-speed perturbations in the average supergranule
• Iterative inversion of synthetic travel times successful at recovering sub-surface profiles of supergranular flows
• Validating Forward Modeling and Inversions of Helioseismic Holography Measurements
• The First Optical Spectra of Wolf Rayet Stars in M101 Revealed with Gemini/GMOS
• Comparison of time-distance inversion methods applied to SDO/HMI Dopplergrams
• Validating time-distance helioseismic inversions for non-separable subsurface profiles of an average supergranule
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• Testing volume integrals of travel-time sensitivity kernels for flows