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A search for acoustic amplitude deficit at the antipodes of sunspots

Peri, Michal L. and Libbrecht, Ken G. (1991) A search for acoustic amplitude deficit at the antipodes of sunspots. Solar Physics, 132 (2). pp. 223-231. ISSN 0038-0938. doi:10.1007/bf00152284.

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We present a search for the acoustic oscillation deficit which may exist at the antipodes of sunspots. Dopplergrams from Big Bear Solar Observatory 1988 helioseismology data were selected for five days on which large sunspots were known to be on the unseen hemisphere of the Sun. Acoustic oscillation amplitudes in the antipodal regions of these sunspots were compared with amplitudes in surrounding quiet-Sun regions. We did not detect a statistically significant acoustic amplitude deficit in our data. Our results indicate that the amplitude deficit at the sunspot antipodal points is limited to no more than 3% of the acoustic amplitude in the region, for solar oscillation modes of spherical harmonic degree l ≲ 200. We conclude that no strong acoustic deficit exists at the antipodes of sunspots. A more sensitive search, requiring more elaborate observations than we have performed, would be desirable in order to determine if a weak acoustic amplitude deficit exists at some level at the antipodes of sunspots, perhaps at higher spatial frequencies of oscillation. The noise level in any signals detected by such observations would probably limit their usefulness as seismic probes. However, information on the lifetimes of solar oscillation modes can be deduced even if no acoustic amplitude deficit is detected.

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Libbrecht, Ken G.0000-0002-8744-3298
Additional Information:© 1991 Springer Verlag. Provided by the NASA Astrophysics Data System. Received 01 August 1990; Revised 04 October 1990; Issue Date April 1991. We are grateful to the observing staff at BBSO for their support in these observations, and to Dr. Martin Woodard for his enlightening comments. The work at BBSO is supported by the National Science Foundation under contracts ATM-8604632 and AST-8657393.
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Subject Keywords:Noise Level; Spatial Frequency; Oscillation Amplitude; High Spatial Frequency; Acoustic Oscillation
Issue or Number:2
Record Number:CaltechAUTHORS:20200702-132221226
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Official Citation:Peri, M.L., Libbrecht, K.G. A search for acoustic amplitude deficit at the antipodes of sunspots. Sol Phys 132, 223–231 (1991).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104212
Deposited By: Tony Diaz
Deposited On:02 Jul 2020 20:29
Last Modified:16 Nov 2021 18:29

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