Helioseismic Imaging of Fast Convective Flows Throughout the Near-Surface Shear Layer

Abstract

Using a new implementation of ring-diagram helioseismology, we ascertain the strength and spatial scale of convective flows throughout the near-surface shear layer. Our ring-diagram technique employs highly overlapped analysis regions and an efficient method of 3D inversion to measure convective motions with a resolution that ranges from $3\mathrm{Mm}$ at the surface to $80\mathrm{Mm}$ at the base of the layer. We find the rms horizontal flow speed to peak at $427\mathrm{m}{\mathrm{s}}^{-1}$ at the photosphere and fall to a minimum of $124\mathrm{m}{\mathrm{s}}^{-1}$ between $20\mathrm{Mm}$ and $30\mathrm{Mm}$. From the velocity amplitude and the dominant horizontal scales seen at each depth, we infer the level of rotational influence on convection to be low near the surface, but transition to a significant level at the base of the near-surface shear layer with a Rossby number varying between 2.2 to as low as 0.1.

12 pages, 5 figures

References in corpus (6)

• Structure and Evolution of Giant Cells in Global Models of Solar Convection
• High-resolution calculation of the solar global convection with the reduced speed of sound technique: II. Near surface shear layer with the rotation
• Meridional Flow in the Solar Convection Zone I: Measurements from GONG Data
• Solar supergranulation revealed by granule tracking
• Structure and evolution of solar supergranulation using SDO/HMI data
• The Sun's Shallow Meridional Circulation

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