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Paper: Center-to-Limb Velocity Systematic in Ring-Diagram Analysis
Volume: 478, Fifty Years of Seismology of the Sun and Stars
Page: 199
Authors: Greer, B.; Hindman, B.; Toomre, J.
Abstract: We use HMI ring-diagram pipeline data to measure a center-to-limb systematic effect seen in velocities. To separate this signal from persistent flow patterns of physical origin, we perform a least-squares fit to the data for each wave mode. We fit a model that includes both the radially symmetric systematic as well as global zonal and meridional flow components. The resulting measurements of the systematic error reveal a smooth trend as a function of both mode frequency and phase speed. The systematic error at 45° from disk center ranges from 20 m/s radially inward to 50 m/s radially outward. The implications for determining global scale meridional flow is discussed.
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