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Analysis of Supergranule Sizes and Velocities Using Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) and Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) DopplergramsCo-temporal Doppler images from Solar and Heliospheric Observatory (SOHO)/ Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) have been analyzed to extract quantitative information about global properties of the spatial and temporal characteristics of solar supergranulation. Preliminary comparisons show that supergranules appear to be smaller and have stronger horizontal velocity flows within HMI data than was measured with MDI. There appears to be no difference in their evolutionary timescales. Supergranule sizes and velocities were analyzed over a ten-day time period at a 15-minute cadence. While the averages of the time-series retain the aforementioned differences, fluctuations of these parameters first observed in MDI data were seen in both MDI and HMI time-series, exhibiting a strong cross-correlation. This verifies that these fluctuations are not instrumental, but are solar in origin. The observed discrepancies between the averaged values from the two sets of data are a consequence of instrument resolution. The lower spatial resolution of MDI results in larger observed structures with lower velocities than is seen in HMI. While these results offer a further constraint on the physical nature of supergranules, they also provide a level of calibration between the two instruments.
Document ID
20140010412
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Williams, Peter E.
(Northern Virgina Community Coll. Annandale, VA, United States)
Pesnell, W. Dean
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Beck, John G.
(Stanford Univ. Stanford, CA, United States)
Lee, Shannon
(San Francisco State Univ. CA, United States)
Date Acquired
August 4, 2014
Publication Date
June 13, 2013
Publication Information
Publication: Solar Physics
Publisher: Springer
Volume: 289
Issue: 1
ISSN: 0038-0938
Subject Category
Solar Physics
Report/Patent Number
GSFC-E-DAA-TN10134
GSFC-E-DAA-TN22814
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Dopplergrams
Helioseismology
SOHO/HMI
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