Mode Parameter Variations from GONG Ring Diagrams: An Update

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Mode Parameter Variations from GONG Ring
Diagrams An Update

• Rachel Howe, NSO

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Synopsis

• Lots of Data!
• Frequency shifts
• Power maps and amplitude shifts
• Summary

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Lots of Data

• We now have about 30 Carrington Rotations of
  GONG data analyzed, contiguous from 1980-2004
  and then 2008-2012.
• 605 days, 114,345 dense-pack cubes.
• Thats 12Tb of data in the tracked velocity
  cubes.
• About 2.5Gb just in parameter tables.

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Frequency Shifts

• One rotation, after subtraction of geometric
  terms, for l652, n3

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Frequency shifts, 25 rotations
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Frequency variations from 25 rotations
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A thought

• Availability of frequencies for many rotations
  should allow detailed study of effect of active
  region evolution on local sound speed profile.

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Parameter sensitivity to B, by rotation

• Linear (left) and quadratic (right) coefficients
  for fits of frequency (top), and amplitude
  (bottom) against B.
• Colored ribbons correspond to different n.
• B from MDI daily synoptic images.

• Amplitude sensitivity seems to vary from rotation
  to rotation.

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Power Maps

• Take each tracked merged image (MI) data cube.
• Perform temporal FFT for each spatial pixel.
• Write 4-plane FITS file containing low-frequency
  (0.5 lt n lt 1.5 mHz), 5-minute (1.5 lt n lt 5.5 mHz)
  and high-frequency (5.5 lt n lt7.5 mHz) total
  power, and mean velocity.
• Gzipped file is 0.25Mb for each dense cube.

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Power Maps

• Mosaic for one day (patches normalized
  separately apparent gradient is artifact of
  overlap order).
• Take mean for each patch
• and subtract fit to distance from disk center.

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Geometric Term in Amplitude

• Power vs distance from disk center, from rings
  (left) and power maps (right).

• Slope does not look constant.

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Slope of power against r, from ring diagram fits.

• Possible correlation with apparent radius?

• Or with B?

Time (days)
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Summary

• GONG data are now plentiful!
• Power maps will be available.
• 5-minute power scaling not completely understood.
  
• Ideas welcome.
• Stay tuned!