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V. Astley (Florida Institute of Technology), R. Komm, R. Howe (National Solar Observatory)
We analyzed a time series of high spatial resolution (.04" per pixel) intensity images of a sunspot region observed on July 15, 2002 with the Swedish Solar Telescope to study the interaction of acoustic modes with small-scale features, such as granules near a sunspot, and their evolution over short time-scales (approximately one hour). The images were taken in G-band intensity with a cadence of 22 seconds. The time series were filtered with Empirical Mode Decomposition to eliminate low frequency power generated by the evolution of solar surface features and a simple 1-D FFT was used to obtain the power spectra in temporal frequency at each spatial location. Preliminary results show a correlation between small-scale structure and frequency-dependent acoustic power emission. Granules show increased power output in the 3 mHz range while the same area shows acoustic suppression at higher frequencies confirming results by other authors. We find that the distribution of acoustic power is spatially very localized especially in penumbral filaments and umbral sub-structures of the sunspot.
This work is carried out through the National Solar Observatory Research Experiences for Undergraduate (REU) site program, which is co-funded by the Department of Defense in partnership with the National Science Foundation REU Program.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.