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Spectrum Estimation in Helioseismology

Spectrum Estimation in Helioseismology. P.B. Stark Department of Statistics University of California Berkeley CA www.stat.berkeley.edu/~stark. Acknowledgements.

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Spectrum Estimation in Helioseismology

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  1. Spectrum Estimation in Helioseismology P.B. Stark Department of Statistics University of California Berkeley CA www.stat.berkeley.edu/~stark

  2. Acknowledgements • Most figures pirated from Global Oscillations Network Group (GONG) and Solar and Heliospheric Observer (SOHO) Solar Oscillations Investigation websites • Much work joint withI.K. Fodor (LLNL), D.O. Gough (Cambridge), Y. Gu (GONG), R. Komm (GONG), C.R. Genovese (Carnegie-Mellon), T. Sekii (Cambridge), M.J. Thompson (Queen Mary and Westfield College).

  3. The Sun Vibrates

  4. The Sun Vibrates • Stellar oscillations known since late 1700s. • Sun's oscillation observed in 1960 by Leighton, Noyes, Simon. • Explanation as trapped acoustic waves by Ulrich, Leibacher, Stein, 1970-1.

  5. Pattern is Superposition of Modes • Like vibrations of spherical guitar string • 3 “quantum numbers” l, m, n • l and m are spherical surface wavenumbers • n is radial wavenumber

  6. Spectrum is very Regular • Explanation as modes predicts details of spectrum • Details confirmed in data by Deubner, 1975 • Over 107 modes predicted • Over 250,000 identified • Will be over 106 soon

  7. “5-minute” oscillations • Takes a few hours for energy to travel through the Sun. • p-mode amplitude ~1cm/s • Brightness variation ~10-7 • Last from hours to months • Excited by convection 40-day time series of mode coefficients, speeded-up by a 42,000. l=1, n=20; l=0, 1, 2, 3 Source: Kosovichev, SOHO

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