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Observations of solar cycle variations in solar p-mode frequencies and splittings

Libbrecht, K. G. and Woodard, M. F. (1990) Observations of solar cycle variations in solar p-mode frequencies and splittings. In: Progress of Seismology of the Sun and Stars. Lecture Notes in Physics. No.367. Springer Berlin Heidelberg , Berlin, Heidelberg, pp. 145-156. ISBN 9783540530916.

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We discuss here two sets of helioseismology data acquired at Big Bear Solar Observatory during the summers of 1986 and 1988. Each data set consists of roughly 60,000 fulldisk Doppler images of the sun, accumulated over a four-month time span. These data clearly show that solar p-mode frequencies change with time, and that the measured frequency shifts Δv = v₈₈ - v₈₆ depend strongly on frequency and only weakly on ℓ for 5 ≤ ℓ ≤ 60. The frequency dependence is well described by Δv ∞ M⁻¹(v), where M(v) is the mode mass for low-ℓ modes. Such a frequency dependence is expected if the effective sound speed perturbation is located predominantly near the solar surface. It should be possible to invert the frequency shift measurements to determine some aspects of the structure of solar activity as a function of depth. The data also show that the even-index splitting coefficients depend strongly on frequency, again being well described by α_(2j) (v) ∞ M⁻¹(v). This functional form is expected if the sound speed perturbation responsible for Δv is localized in solar latitude. Latitude inversions of the time-dependent splitting and Δv measurements show that the perturbation is strongest in the active latitudes, but includes a weak polar component.

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Libbrecht, K. G.0000-0002-8744-3298
Additional Information:© Springer-Verlag 1990. We are grateful to the cast of observers at Big Bear Solar Observatory who diligently carried out these observations, particularly Bill Marquette and Randy Fear. We also thank Peter Goldreich and Pawan Kumar for many informative discussions. These data were analyzed in part using the facilities of the San Diego Supercomputer Center, and the work was supported in part by NSF ATM-8604632 and NSF PYI award AST-8657393.
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Subject Keywords:Frequency Shift; Solar Cycle; Solar Minimum; Solar Latitude; Limb Measurement
Series Name:Lecture Notes in Physics
Issue or Number:367
Record Number:CaltechAUTHORS:20201008-112317386
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105925
Deposited By: George Porter
Deposited On:08 Oct 2020 20:36
Last Modified:16 Nov 2021 18:47

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