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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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