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

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