HMI H8: Flows TimeDistance

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HMI H8 Flows / Time-Distance

• L. Gizon
• A. Birch, T. Duvall, J. Jackiewicz, R. Larsen,
  M. Rempel

• SMALL-AMPLITUDE STEADY OR SLOWLY TIME-VARYING
  FLOWS
• A LINEAR PROBLEM. Typically less than 500 m/s
• Travel-time measurement procedure not optimal
  yet
• Kernels okay given 1
• Noise covariance okay given 1.
• Inversion conceptually okay, but lots of
  regularization parameters and intensive
  computations to cover the whole solar disk (hmi).
  
• All step must be consistent!
• Need a complete list of kernels (not just
  flows)!
• Systematic effects MTF (okay if known), los
  (okay), foreshortening (okay). Note that we
  cannot correct the data before inversions we
  need to deal with this if we care about
  resolution at wavelength scales.
• LARGER AMPLITUDE / INTERMITTENT FLOWS / SUNSPOT
  FLOWS quite scary.

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Travel time kernels for flowsF modes, near disk
center
Includes subtle effects like doppler shift of
sources, damping in a co-moving frame
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Effect of line-of-sight projectionLatitude0
deg, Longitude 75 deg from central meridian
Disk center
Poster Jackiewicz
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3D f mode kernel for Ux Vertical slice through
observation points.
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Noise correlation
Jackiewicz. See Gizon Birch 2004
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Correlation vertical vorticity horizontal div
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Larger spatial scales ring and TD analyses are
consistent (Hindman et al. 2003)
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F-mode TD div maps advection of supergranulation
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Comparison with model (Rempel, after Spruit)
MODEL 10 Mm deep /- 5 m/s
DATA SG Layer /- 4 m/s
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MODEL 50 Mm deep /- 1 m/s
DATA 50 Mm deep /- 2 m/s. P-mode travel
times (Beck)
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vy const amplicos(w t phase)