Comparison of Shravans artificial data with GONG data preliminary results

1
Comparison of Shravans artificial data with GONG
data (preliminary results)

• Olga Burtseva and Shukur Kholikov (NSO/GONG)

LoHCo meeting Boulder, 9 November 2006
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ARTificial data GONG data

• Raw 512?512 pixels images in (?,?) coordinates
  -90? ? ? ? 90?
• 0? ? ? ? 180? (front side) 181? ? ? ?
  360? (far side)
• ? - range 0 - 192
• Duration 1024 min.
• Remaped 700?512 pixels in (sin ?,?)
  coordinates
• No rotation
• Filtered with Gaussian function FWHM 2.0 mHz,
  ?0 3.0 mHz

• Raw 800?800 pixels velocity images, two days in
  January 2004
• Duration 1024 min.
• Remaped 700?512 pixels in (sin ?,?) coordinates
• Rotation subtracted
• Filtered with Gaussian function FWHM 2.0 mHz,
  ?0 3.0 mHz

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Cross-correlation function
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Envelope travel time
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Envelope travel time
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Envelope travel time
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Travel times difference
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Travel times difference
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Conclusion

• Cross-correlation function of the ART data looks
  fine, multiple bounces are visible
• Travel times of the ART data are systematically
  6-7 min. shorter than the GONG travel times
• Travel times of 2nd and 3rd skips of the ART data
  are not exactly 2 and 3 times longer than 1st
  skip travel time
• We found 1 min. shift in travel times between
  ingoing and outgoing waves for the ART data
• Difference between phase and envelope times is
  more or less constant in 4 skips of the ART data,
  while it is not the case for the GONG data