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Near-Surface Flow Fields Deduced Using Correlation Tracking and Time-Distance AnalysisNear-photospheric flow fields on the Sun are deduced using two independent methods applied to the same time series of velocity images observed by SOI-MDI on SOHO. Differences in travel times between f modes entering and leaving each pixel measured using time-distance helioseismology are used to determine sites of supergranular outflows. Alternatively, correlation tracking analysis of mesogranular scales of motion applied to the same time series is used to deduce the near-surface flow field. These two approaches provide the means to assess the patterns and evolution of horizontal flows on supergranular scales even near disk center, which is not feasible with direct line-of-sight Doppler measurements. We find that the locations of the supergranular outflows seen in flow fields generated from correlation tracking coincide well with the locations of the outflows determined from the time-distance analysis, with a mean correlation coefficient after smoothing of bar-r(sub s) = 0.840. Near-surface velocity field measurements can used to study the evolution of the supergranular network, as merging and splitting events are observed to occur in these images. The data consist of one 2048-minute time series of high-resolution (0.6" pixels) line-of-sight velocity images taken by MDI on 1997 January 16-18 at a cadence of one minute.
Document ID
20000021166
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
DeRosa, Marc
(Colorado Univ. Boulder, CO United States)
Duvall, T. L., Jr.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Toomre, Juri
(Colorado Univ. Boulder, CO United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Solar Physics
Funding Number(s)
CONTRACT_GRANT: NAG5-3077
CONTRACT_GRANT: NSF ATM-97-31676
CONTRACT_GRANT: NAG5-8133
CONTRACT_GRANT: NAG5-7996
Distribution Limits
Public
Copyright
Other

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