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Time-Distance Study of Isolated Sunspots: Enhancing Helioseismology Techniques

This study presents a time-distance analysis of isolated sunspots, aiming to refine the techniques used in helioseismology for the Solar Dynamics Observatory (SDO) mission. We utilized algorithms for travel time estimation and inversion, utilizing open-source ANSI C code for our analyses. Through extensive data collection from the EGSO Sunspot Solar Feature catalogue and MDI level-2 data, we identified and tracked several sunspots to improve understanding of their structure and dynamics. Our findings emphasize the need for more detailed data processing and noise statistics to enhance the reliability of sound-speed profiles.

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Time-Distance Study of Isolated Sunspots: Enhancing Helioseismology Techniques

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  1. Time Distance Study of Isolated Sunspots S. Zharkov, C.J. Nicholas, M.J. Thompson Nice LHS Workshop, September, 2006

  2. supporting SDO mission in UK and worldwide • Sheffield algorithms: local helioseismology: travel time maps and inversion • code written in ANSI C, open source • current level of implementation: • travel-time estimation • inversion • testing Nice LHS Workshop, September, 2006

  3. Data • Using EGSO Sunspot Solar Feature catalogue we identified a number of isolated sunspots that had no other sunspots within 10 heliographic degrees radius. • Locating the available MDI level-2 data we have selected 6 sunspots comprising Active Regions • Using EGSO SFC and solarmonitor.org we track each region for several rotations Nice LHS Workshop, September, 2006

  4. Time-Distance • level2 MDI tracked derotated data (full disk resolution) • level 1.8 full disk data – tracked and derotated using Postel azimuthal projection and Snodgrass formula for derotation • pre-processing • Instrument MTF, low- & high-pass filtering, phase-speed filtering, f-mode filter • center to annulus geometry • travel times measured by Gabor wavelet fitting • Fresnel zone sensitivity kernels (Jensen & Pijpers, 2003) • 12 skip-distance inverted to 14 depths using Multi-Channel Deconvolution (Jensent et al, 1998) Nice LHS Workshop, September, 2006

  5. Inversion: Multichannel deconvolution Nice LHS Workshop, September, 2006

  6. Depth cuts NOAA8038 Nice LHS Workshop, September, 2006

  7. Nice LHS Workshop, September, 2006

  8. 0.36 Mm Nice LHS Workshop, September, 2006

  9. 6.4 Mm Nice LHS Workshop, September, 2006

  10. 0-crossing thru max flux point Nice LHS Workshop, September, 2006

  11. AR statistics Nice LHS Workshop, September, 2006

  12. next: more data? Nice LHS Workshop, September, 2006

  13. Questions & conclusions • real? • must include noise statistics to derive more accurate and reliable sound-speed profile • need more detailed kernels - looking forward to HELAS kernel facility (filter dependent) • cookie cutter test Nice LHS Workshop, September, 2006

  14. thank you Nice LHS Workshop, September, 2006

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