Time Distance Study of Isolated Sunspots

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Time Distance Study of Isolated Sunspots

• S. Zharkov, C.J. Nicholas,
• M.J. Thompson

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• supporting SDO mission in UK and worldwide
• Sheffield algorithms local helioseismology
  travel time maps and inversion
• code written in ANSI C, open source
• current level of implementation
• travel-time estimation
• inversion
• testing

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Data

• Using EGSO Sunspot Solar Feature catalogue we
  identified a number of isolated sunspots that had
  no other sunspots within 10 heliographic degrees
  radius.
• Locating the available MDI level-2 data we have
  selected 6 sunspots comprising Active Regions
• Using EGSO SFC and solarmonitor.org we track each
  region for several rotations

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Time-Distance

• level2 MDI tracked derotated data (full disk
  resolution)
• level 1.8 full disk data tracked and derotated
  using Postel azimuthal projection and Snodgrass
  formula for derotation
• pre-processing
• Instrument MTF, low- high-pass filtering,
  phase-speed filtering, f-mode filter
• center to annulus geometry
• travel times measured by Gabor wavelet fitting
• Fresnel zone sensitivity kernels (Jensen
  Pijpers, 2003)
• 12 skip-distance inverted to 14 depths using
  Multi-Channel Deconvolution (Jensent et al, 1998)

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Inversion Multichannel deconvolution
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Depth cuts NOAA8038
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(No Transcript)
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0.36 Mm
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6.4 Mm
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0-crossing thru max flux point
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AR statistics
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next more data?
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Questions conclusions

• real?
• must include noise statistics to derive more
  accurate and reliable sound-speed profile
• need more detailed kernels - looking forward to
  HELAS kernel facility (filter dependent)
• cookie cutter test

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• thank you