Magnetic Fields at Mt. Wilson and MDI

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Magnetic Fields atMt. Wilson and MDI
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The 150-foot Tower Spectrograph Measures 12 line
pairs simultaneously

• The long-term program uses 5250.
• The full coverage of 6768 allows modeling of MDI.
• The Na D2 line permits interesting studies of
  height dependence.

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The Fluxtube Magnetic Structure Complicates
Interpretation

• This diagram shows the relationship between the
  magnetic structure and our points of observation.

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Comparison between MWO and MDI

• We interpolate and bin the MDI magnetogram to
  match the temporal/spatial location of MWO
  pixels. This is MWO as seen by MDI.
• We reconstruct the 6768 line profile and apply
  model MDI filters to it to find a MWO-modeled
  field. This is MDI as seen by MWO.

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Temporal trends near disk center

• Approximately 1200 MWO/MDI intercomparisons have
  been constructed to yield a scale factor between
  MDI and MWO.
• These two are for near disk center areas.

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Temporal trends near the limb.

• The outer sections of the solar image have been
  divided into quadrants. The scatter is much
  larger here and there are fewer points per image.

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Magnetic geometries are not all vertical.

• The potential field solutions used in the
  Wang-Sheeley model assume the field geometry is
  vertical at the photosphere. This is
  demonstrably an inaccurate assumption.

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The geometry of the rotating sun and magnetic
fields
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Solar rotation and magnetic geometry.
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Neutral lines and tilt map
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Comparison to TRACE