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Paper: Solar-Cycle Variation of Subsurface Zonal Flow Derived from Ring-Diagram Analysis
Volume: 478, Fifty Years of Seismology of the Sun and Stars
Page: 217
Authors: Komm, R.; Howe, R.; González Hernández, I.; Hill, F.; Bogart, R. S.; Haber, D.
Abstract: We study the solar-cycle variation of the zonal flow in the near-surface layers of the solar convection zone from the surface to a depth of 16 Mm. We have analyzed Global Oscillation Network Group (GONG) and Helioseismic and Magnetic Imager (HMI) Dopplergrams with the ring-diagram analysis covering about 12 years combined. The zonal flow varies with the solar cycle showing faster-than-average flows equatorward of the mean latitude of activity and slower-than-average flows on the poleward side. The bands of fast zonal flow appear at mid-latitudes about two years before magnetic activity of cycle 24 is seen. The poleward branch of this variation is visible as bands of fast zonal flow near 50° latitude in both HMI and GONG data.
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