Comparison of Large-Scale Flows on the Sun Measured by Time-Distance Helioseismology and Local Correlation Tracking |
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Authors: | Michal ?vanda Junwei Zhao Alexander G Kosovichev |
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Institution: | (1) Ondřejov Observatory, Astronomical Institute of Academy of Sciences, Ondřejov, 251 65, Czech Republic;(2) Astronomical Institute, Charles University, V Holešovičkách 2, Prague, 182 00, Czech Republic;(3) W.W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085, USA |
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Abstract: | We present a direct comparison between two different techniques: time-distance helioseismology and a local correlation tracking
method for measuring mass flows in the solar photosphere and in a near-surface layer. We applied both methods to the same
dataset (MDI high-cadence Dopplergrams covering almost the entire Carrington rotation 1974) and compared the results. We found
that, after necessary corrections, the vector flow fields obtained by these techniques are very similar. The median difference
between directions of corresponding vectors is 24°, and the correlation coefficients of the results for mean zonal and meridional
flows are 0.98 and 0.88, respectively. The largest discrepancies are found in areas of small velocities where the inaccuracies
of the computed vectors play a significant role. The good agreement of these two methods increases confidence in the reliability
of large-scale synoptic maps obtained by them. |
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Keywords: | Sun: surface flows Time-distance helioseismology Local correlation tracking |
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