Astronomy and Astrophysics – Astronomy
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009apj...696l.106c&link_type=abstract
The Astrophysical Journal Letters, Volume 696, Issue 1, pp. L106-L109 (2009).
Astronomy and Astrophysics
Astronomy
9
Sun: Activity, Sun: Helioseismology, Sun: Interior, Sunspots
Scientific paper
The power of solar acoustic waves in magnetic regions is lower relative to the quiet Sun. Absorption, emissivity reduction, and local suppression of acoustic waves contribute to the observed power reduction in magnetic regions. We propose a model for the energy budget of acoustic waves propagating through a sunspot in terms of the coefficients of absorption, emissivity reduction, and local suppression of the sunspot. Using the property that the waves emitted along the wave path between two points have no correlation with the signal at the starting point, we can separate the effects of these three mechanisms. Applying this method to helioseismic data filtered with direction and phase-velocity filters, we measure the fraction of the contribution of each mechanism to the power deficit in the umbra of the leading sunspot of NOAA 9057. The contribution from absorption is 23.3 ± 1.3%, emissivity reduction 8.2 ± 1.4%, and local suppression 68.5 ± 1.5%, for a wave packet corresponding to a phase velocity of 6.98 × 10-5 rad s-1.
Chou Dean-Yi
Liang Zhi-Chao
Sun Ming-Tsung
Yang Ming-Hsu
Zhao Hui
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