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Far-side Imaging of Active Regions: Latest Developments Irene González Hernández and the GONG andHMI far-side teams National Solar Observatory, Tucson, AZ Northwest Research Associates (CORA), Boulder, CO Stanford University, Stanford, CA. Introduction to far-side seismic holography

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  1. Far-side Imaging of Active Regions: Latest DevelopmentsIrene González Hernández and the GONG andHMI far-side teamsNational Solar Observatory, Tucson, AZNorthwest Research Associates (CORA), Boulder, COStanford University, Stanford, CA

  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. Improving the far-side monitor • Detecting medium size active regions  Reducing the noise by combining consecutive, non-overlapping maps • Calibrating in terms of magnetic field strength ( using the relationship found by Gonzalez Hernandez, Hill, Lindsey 2009, ApJ) • Removing the Solar Cycle variation as described by Gonzalez Hernandez, Scherrer and Hill (ApJ, 2010) • Confidence Level (…. Space Weather Journal, 2010) • Adding extra info on date of return and NOAA previous number if existed

  7. Calibrating the far-side signal

  8. Calibrating the far-side signal González Hernández, I.; Hill, F.; Lindsey, C. Calibration of Seismic Signatures of Active Regions on the Far Side of the Sun 2007ApJ...669.1382G

  9. Confidence Level REFERENCES González Hernández, I.; Scherrer, P.; Hill, F. A New Way to Infer Variations of the Seismic Solar Radius 2009ApJ...691L..87G <González Hernández, I.; Hill, F.; Lindsey, C. Calibration of Seismic Signatures of Active Regions on the Far Side of the Sun 2007ApJ...669.1382G Fontenla, J. M.; Quémerais, E.; González Hernández, I.; Lindsey, C.; Haberreiter, M Solar irradiance forecast and far-side imaging 2009AdSpR..Pérez Hernández, F.; González Hernández, I.Green's Functions for Far-Side Seismic Images: A Polar-Expansion Approach 2010ApJ...711..853P I. González Hernández, F. Hill, P. H. Scherrer, C. Lindsey, and D. C. BraunSpace Weather, 8, S06002, doi:10.1029/2009SW000560, 2010

  10. New Calibrated Far-side maps C. Long. Latitude Phase-shift Prob. Effective-Area Date-of-return Front-side-number 203.039993 -19.876875 -0.159418 87 84.239998 20100911 NOAA 11100

  11. New Calibrated Far-side maps Helioseismic far-side maps on the left and simultaneous STEREO behind observations of AR NOAA 11026 before it appeared on the front side of the Sun on September 21 2009

  12. Further Improvements • Sensitivity variation with location !! • Detecting smaller active regions (signal-to-noise) • Duty cycle • Hmi combination • Area estimation • Show current calibration • Talk about Effective area • Front side study • Error estimation • Integrated Index • Polarity

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

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

  17. 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

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

  19. The Farside Magnetic Index Comparison with front-side indexes:. The graphic below shows simultaneous observations of Ly-α (lasp.colorado.edu), F10 (www.ngdc.noaa.gov), the calculated Mount Wilson Sunspot Index (www.astro.ucla.edu) and the Far Side Magnetic Index. The sequence spans from October 2002 to December 2006. The different indexes have been scaled and shifted to aid the comparison. In collaboration with K. Jain, W. K. Tobiska and F. Hill

  20. Solar cycle variation

  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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