Global effects of local sound-speed perturbations in the sun

A theoretical study

Shravan Hanasoge, T. P. Larson

    Research output: Contribution to journalArticle

    Abstract

    We study the effect of localized sound-speed perturbations on global mode frequencies by applying techniques of global helioseismology to numerical simulations of the solar acoustic wave field. Extending the method of realization-noise subtraction (e.g., Hanasoge, Duvall, and Couvidat, Astrophys. J. 664, 1234, 2007) to global modes and exploiting the luxury of full spherical coverage, we are able to achieve very highly resolved frequency differences that are then used to study sensitivities and the signatures of the thermal asphericities. We find that i) global modes are almost twice as sensitive to sound-speed perturbations at the bottom of the convection zone in comparison to anomalies well inside the radiative interior (r≲0.55R ), ii) the m degeneracy is lifted ever so slightly, as seen in the a coefficients, and iii) modes that propagate in the vicinity of the perturbations show small amplitude shifts. Through comparisons with error estimates obtained from Michelson Doppler Imager (MDI; Scherrer et al., Solar Phys. 162, 129, 1995) observations, we find that the frequency differences are detectable with a sufficiently long time series (70-642 days).

    Original languageEnglish (US)
    Pages (from-to)91-100
    Number of pages10
    JournalSolar Physics
    Volume251
    Issue number1-2
    DOIs
    StatePublished - Sep 1 2008

    Fingerprint

    theoretical study
    sun
    perturbation
    acoustics
    acoustic wave
    wave field
    asphericity
    helioseismology
    convection
    subtraction
    time series
    anomaly
    signatures
    anomalies
    simulation
    effect
    speed
    sound
    sensitivity
    shift

    Keywords

    • Helioseismology: Direct modeling
    • Interior: Convective zone
    • Interior: Tachocline
    • Waves: Acoustic

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Global effects of local sound-speed perturbations in the sun : A theoretical study. / Hanasoge, Shravan; Larson, T. P.

    In: Solar Physics, Vol. 251, No. 1-2, 01.09.2008, p. 91-100.

    Research output: Contribution to journalArticle

    Hanasoge, Shravan ; Larson, T. P. / Global effects of local sound-speed perturbations in the sun : A theoretical study. In: Solar Physics. 2008 ; Vol. 251, No. 1-2. pp. 91-100.
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