Local helioseismology at small scales

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Local helioseismologyat small scales
Takashi Sekii (NAOJ)
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I am talking about

• How SDO and Solar-B can work together for
  high-resolution local helioseismology, for
  subphotospheric dynamics
• What kind of challenges are ahead

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Solar-B

• A J/US/UK/European collaboration
• To be launched in September 2006

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Solar Optical Telescope

• 50-cm Solar Optical Telescope (SOT) produces
  high-resolution Dopplergrams that can be used for
  local helioseismology
• FOV narrow but high spatial resolution
• Not suited for probing deep layers
• (Horizontally) high-resolution view of the solar
  interior
• For more details, ask Katsukawa-san

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HMI and SOT

• Spatial resolution and FOV
• HMI/SDO 1 arcsec, the entire disc
• SOT/Solar-B 0.2 arcsec, 328x164()
• size of individual flux tubes 100-300km (0.2
  arcsec150km)
• HMI/SOT Simultaneous observation will be very
  useful as it combines broader coverage (HMI) and
  higher resolution (SOT)

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High-resolution local helioseismology (1/4)

• Is it worth doing?
• Is there any wavefield power at such a small
  scale?

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High-resolution local helioseismology (2/4)

• MDI high-resolution power spectrum
• No resonant p modes above l2000
• The f-mode frequency ? sqrt(l)

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High-resolution local helioseismology (3/4)

• Sekii et al 2001 MDII(left) versus La Palma
  SVST G-band (right, Berger et al 1998)

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High-resolution local helioseismology (4/4)

• La Palma result shows improvement in (mainly
  p-mode) time-distance S/N in lt10,000 km range,
  down to lt1,000km
• Local helioseismology with high-degree f modes is
  an obvious thing to do, but p-mode seismology
  will also benefits from higher-resolution

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Challenges (1/2)

• Propagation of waves in magnetized fluid when
  wavelength is similar to the size of individual
  flux tubes
• And use them for diagnostic purpose
• Can we observe kernels? (Duvall, Gizon Birch)

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Challenges (2/2)

• What is the smartest way to merge f-mode data and
  p-mode data (or do we just merge them)
• Similarly, how do we merge HMI data and SOT data?
• T-d analysis in magnetic regions
• Comparing magnetic-line data (HMI SOT) and
  non-magnetic-line data (SOT) should be useful
  (not just for HR stuff!)