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Sounding the Sun: HelioseismologyColloquium
|Speaker: ||Professor Philip B. Stark, Department of Statistics, UC Berkeley|
|Location: ||693 Kerr|
|Start time: ||Mon, Apr 24 2000, 4:10PM|
Helioseismology is the study of the interior of the sun from its acoustic
vibrations, which have a characteristic period of about 5 minutes.
Infering solar structure and kinematics from the frequencies of solar
oscillations is an inverse problem that can be addressed with a number
of statistical tools. I will give an overview of helioseismology,
focusing on statistical problems in estimating the oscillation frequencies
from the fundamental observations. The basic data are the intensities of light
at various frequencies in each pixel of a CCD camera, measured once a
minute. These spatio-temporal series have gaps, caused by malfunctions,
birds in the field of view, routine maintenance, the use of the
telescope for other kinds of observations, etc. I will present an approach to
mitigating the effect of the gaps on estimates of the spectrum of
oscillations: multitaper spectrum estimates using gap-adapted tapers.
The approach is computationally efficient, and improves the reliability of
estimates of the oscillation frequencies and allows the frequencies of more
solar modes to be estimated, compared with methods used previously.
The approach was adopted recently by the Global Oscillations Network
Group (GONG), a network of six solar telescopes that span the globe at
mid-latitudes, for their standard data-reduction pipeline. This work
is joint with Imola Fodor (Lawrence Livermore National Laboratory) and
the GONG project team (National Solar Observatory, Tucson).