Inversions for Average Supergranular Flows Using Finite-frequency Kernels

Abstract

I analyse the maps recording the travel-time shifts caused by averaged plasma anomalies under an "average supergranule", constructed by means of statistical averaging over 5582 individual supergranules with large divergence signals detected in two months of HMI Dopplergrams. By utilising a three-dimensional validated time-distance inversion code, I measure the peak vertical velocity of 117+/-2 m/s in depths around 1.2 Mm in the centre of the supergranule and root-mean-square vertical velocity of 21 m/s over the area of the supergranule. A discrepancy between this measurement and the measured surface vertical velocity (a few m/s) can be explained by the existence of the large-amplitude vertical flow under the surface of supergranules with large divergence signals, recently suggested by Duvall & Hanasoge (2012).

5 pages, 5 figures, accepted for Astrophysical Journal Letters

References in corpus (4)

• Linear Sensitivity of Helioseismic Travel Times to Local Flows
• High-resolution mapping of flows in the solar interior: Fully consistent OLA inversion of helioseismic travel times
• Subsurface Supergranular Vertical Flows as Measured Using Large Distance Separations in Time-Distance Helioseismology
• Supergranules as Probes of Solar Convection Zone Dynamics

Cited by in corpus (16)

• Seismic Sounding of Convection in the Sun
• Comparison of solar surface flows inferred from time--distance helioseismology and coherent structure tracking using HMI/SDO observations
• Validating Time-Distance Helioseismology With Realistic Quiet Sun Simulations
• Additional Evidence Supporting a Model of Shallow, High-Speed Supergranulation
• Full Waveform Inversion of Solar Interior Flows
• Helioseismic Investigation of Modeled and Observed Supergranule Structure
• The Quest to Understand Supergranulation and Large-Scale Convection in the Sun
• Time-Distance Helioseismology of Two Realistic Sunspot Simulations
• Issues with time--distance inversions for supergranular flows
• Combined helioseismic inversions for 3D vector flows and sound-speed perturbations
• Plasma flows and sound-speed perturbations in the average supergranule
• Probabilistic Inversions for Time-Distance Helioseismology
• Validating Forward Modeling and Inversions of Helioseismic Holography Measurements
• Iterative inversion of synthetic travel times successful at recovering sub-surface profiles of supergranular flows
• Observational characterisation of large-scale transport and horizontal turbulent diffusivity in the quiet Sun
• Exploiting solar visible-range observations by inversion techniques: from flows in the solar subsurface to a flaring atmosphere