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Far-side Imaging and Activity Irene González Hernández and the GONG and MDI far-side teams National Solar Observatory, Tucson, AZ Stanford University, Stanford, CA Northwest Research Associates (CORA), Boulder, CO. Introduction to far-side seismic holography Improving the far-side maps

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  1. Far-side Imaging and ActivityIrene González Hernández and the GONG and MDI far-side teamsNational Solar Observatory, Tucson, AZStanford University, Stanford, CANorthwest Research Associates (CORA), Boulder, CO

  2. Introduction to far-side seismic holography • Improving the far-side maps • Calibrating the seismic signal • Success Rate Variation of the mean phase with the solar cycle ! • Improving the signal to noise • Future work and conclusions Contents

  3. Pupil • Helioseismic imaging of sunspots at their antipodes. Lindsey, C. & Braun, D.C, 1990, SoPh. • Seismic Images of the Far Side and Interior of the Sun Lindsey, C. & Braun, D.C, 2000, Science. Helioseismic Imaging of the Farside

  4. Phase of the Correlation Helioseismic Imaging of the Farside

  5. MDI (HMI) GONG Users able to subscribe to alerts > % FS00543 |B| Time Distance ( HMI + GONG) Improving the far-side monitor 85 %

  6. AR10808 Active Region NOAA-10923 Oct 31 -> Nov 10 2006 AR10923 sin(latitude) Calibrating the far-side signal Active Region NOAA-10808 Aug 29 -> Sep 9 2005 sin(latitude) Carrington Longitude

  7. Calibrating the far-side signal

  8. Calibrating the far-side signal

  9. “far-side” imaging of the near side 1 x 3 skip method actually extends well onto the near side!

  10. Success rate MDI GONG MDI + GONG

  11. Success Rate

  12. Why the improvement? • Different length of time series • Duty Cycle • Phase correction • Bad data

  13. Why the improvement? • Phase Correction

  14. Why the improvement? • Mean Phase --> Temporal Variation

  15. Variation of the seismic solar radius • Solar acoustic radius variation --> solar cycle variation Kholikov & Hill, 2008, SoPh

  16. Solar cycle variation • Mean Phase --> Solar Cycle variation --> Solar acoustic radius variation (??)

  17. Solar cycle variation • Mean Phase --> Solar Cycle variation --> Solar acoustic radius variation--> Localized to surface magnetic areas (?)

  18. Far-side maps from time-distace Time distance Seismic holography September 03 2005 NOAA 10808 GONG MDI Courtesy of Junwei Zhao

  19. Artifacts • Thomas Hartlep,Junwei Zhao Nagi N. Mansour, and Alexander G. Kosovichev Validating Time-Distance Far-Side Imaging of Solar Active Regions through Numerical Simulations ApJ, 689:1373–1378, 2008 December 20

  20. Why the improvement? GONG MDI 060902 060902 060903 060903

  21. Can we improve the Green’s Functions? • More realistic model --> Collaboration with Fernando Pérez at the IAC • Empirical calibration of the dispersion • Dispersion for several bounces

  22. Users able to subscribe to alerts > % FS00543 MDI GONG |B| 85 % Time Distance ( HMI + GONG) Conclusions and Future work • Improving the Maps • Calibration --> extending to the front side • Success Rate --> more accurate determination • Better Signal to Noise --> HMI data/ combination of ray paths / green’s functions / artifacts • Understanding Solar Cycle variations !!!

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