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 with I.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. 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 10 7 modes predicted Over 250,000 identified Will be over 10 6 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