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POLAR CORONAL HOLES

POLAR CORONAL HOLES. Shea A. Hess Webber W. Dean Pesnell Summer 2010. A Link to Predicting Solar Maximum. Perimeter Tracking Method. SOHO EIT images, 3 wavelengths Picking boundary points along limb Limb brightening Thresholding Tracking points over Harvey Rotation

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POLAR CORONAL HOLES

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  1. POLAR CORONAL HOLES Shea A. Hess Webber W. Dean Pesnell Summer 2010 A Link to Predicting Solar Maximum

  2. Perimeter Tracking Method • SOHO EIT images, 3 wavelengths • Picking boundary points along limb • Limb brightening • Thresholding • Tracking points over Harvey Rotation • Differential rotation • Approximately 27 days at equator (Carrington Rotation) • Approximately 33 days at the poles (Harvey Rotation) • Trig fit to resolve areas with uncertainties

  3. 304 Å (He II) in red 171 Å (Fe XI/X) in blue 195 Å (Fe XII) in green Scale Height: H = kT/Mg k = Boltzmann constant T = Temperature (in K) M = mean molecular mass of particles g = acceleration of gravity Different ions at varying temperatures equate to different heights in the solar atmosphere. 304 Å  upper chromosphere 171 Å and 195 Å  corona

  4. Perimeter Tracking Method • SOHO EIT images, 3 wavelengths • Picking boundary points along limb • Limb brightening • Thresholding • Tracking points over Harvey Rotation • Differential rotation • Approximately 27 days at equator (Carrington Rotation) • Approximately 33 days at the poles (Harvey Rotation) • Trig fit to resolve areas with uncertainties

  5. Perimeter Tracking Method • SOHO EIT images, 3 wavelengths • Picking boundary points along limb • Limb brightening • Thresholding • Tracking points over Harvey Rotation • Differential rotation • Approximately 27 days at equator (Carrington Rotation) • Approximately 33 days at the poles (Harvey Rotation) • Trig fit to resolve areas with uncertainties

  6. Perimeter Tracking Method • SOHO EIT images, 3 wavelengths • Picking boundary points along limb • Limb brightening • Thresholding • Tracking points over Harvey Rotation • Differential rotation • Approximately 27 days at equator (Carrington Rotation) • Approximately 33 days at the poles (Harvey Rotation) • Trig fit to resolve areas with uncertainties

  7. Southern Polar Coronal Hole Average

  8. Northern Polar Coronal Hole Average

  9. Updated Data • Threshold adjustment in all wavelengths • Extended data time series from 2007 to 2010 • 304 Å comparison with Nishu

  10. Further Work • Fine-tune thresholds • Adjust programs to run by HR vs. by year • Convert programs to work with SDO data • Do similar image analysis with magnetograms and compare • Re-address solar B angle periodicity

  11. Acknowledgments W. Dean Pesnell NishuKarna Peter Williams Mike Kirk Alex Young Most of the Solar Physics scientists… Background Image: SDO AIA Composite Image Data Images: SOHO EIT Images

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