Asymmetries of solar oscillation line profiles

Duvall, T. L.; Jefferies, S. M.; Harvey, J. W.; Osaki, Yoji; Pomerantz, M. A.

doi:10.1086/172800

Cited by 151 publications

(125 citation statements)

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“…The amount of ridge shift can be as large as half of the ridge-width for p 1 , p 2 , and p 3 ridges at the frequency of 5.0 and 6.0 mHz, as can be seen in Figure 4c and d. It can also be found in Figure 4 that the modal ridge line-profile asymmetry is more significant in the power spectrum from the sunspot than from the quiet-Sun region. It is well known that the modal ridges obtained from Doppler observations exhibit line-profile asymmetries (Duvall et al, 1993a), and this asymmetry is believed to be caused by correlated noise (Nigam et al, 1998;Georgobiani, Stein, and Nordlund, 2003). It is not immediately clear whether the more prominent lineprofile asymmetries in sunspots can be explained by more substantial correlated noise observed in these areas.…”

Section: Resultsmentioning

confidence: 99%

Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

Zhao

Chou

2012

Sol Phys

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The continuous high spatial-resolution Doppler observation of the Sun by Solar Dynamics Observatory / Helioseismic and Magnetic Imager allows us to compute helioseismic k-ω power-spectrum diagram using only oscillations inside a sunspot. Individual modal ridges can be clearly seen with reduced power in the k-ω diagram constructed by use of 40-hour observation of a stable and round sunspot. Comparing with the k-ω diagram obtained from a quiet-Sun region, inside the sunspot the f -mode ridge gets more power reduction than p-mode ridges, especially at high wavenumber. The p-mode ridges all shift toward lowerwavenumber (or higher-frequency) areas for a given frequency (or wavenumber), implying an increase of phase velocity beneath the sunspot. This probably results from acoustic waves' travel across the inclined magnetic field of the sunspot penumbra. Line-profile asymmetries exhibited in the p-mode ridges are more significant in the sunspot than in quiet Sun. Convection inside the sunspot is also highly suppressed, and its characteristic spatial scale is substantially larger than the typical convection scale of quiet Sun. These observational facts demand a better understanding of magnetoconvection and interactions of helioseismic waves with magnetic field.

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Section: Resultsmentioning

confidence: 99%

Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

Zhao

Chou

2012

Sol Phys

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“…The p-mode oscillations of the Sun have resonant peak shapes in the frequency power spectrum that depart from a symmetric, Lorentzian form ( Duvall et al 1993). Asymmetry is present typically at the few-percent level.…”

Section: Introductionmentioning

confidence: 99%

On the Variation of the Peak Asymmetry of Low‐ℓ SolarpModes

Jiménez-Reyes

Chaplin

Elsworth

et al. 2007

ApJ

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The resonant peaks of solar p modes show small amounts of asymmetry in frequency. Here, we use five independent sets of contemporaneous data, collected over a '8 yr period, to investigate whether peak asymmetry in low angular degree p modes changes over the solar activity cycle. Three of the data sets are from instruments on board the ESA /NASA SOHO spacecraft (GOLF, MDI, and VIRGO/SPM ); and two are from ground-based networks (BiSON and GONG). Evidence for variation in asymmetry, well correlated with the activity cycle, is uncovered in the GOLF and BiSON Doppler velocity data. Suggestions of a similar trend are present in the GONG Doppler velocity data. Apparent changes in the MDI Doppler velocity data are somewhat less significant. Meanwhile, analysis of the SPM intensity data failed to uncover any evidence for significant change of the asymmetry parameter.

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“…Duvall et al 1993;Toutain et al 1998;Chaplin & Appourchaux 1999). This is believed to be a consequence of the localized nature of the source which drives the oscillations (e.g.…”

Section: Introductionmentioning

confidence: 99%

Structure of the Solar Core: Effect of Asymmetry of Peak Profiles

Basu¹,

Turck‐Chièze²,

Berthomieu³

et al. 2000

ApJ

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Recent studies have established that peaks in solar oscillation power spectra are not Lorentzian in shape, but have a distinct asymmetry. Fitting a symmetric Lorentzian profile to the peaks therefore produces a shift in frequency of the modes. Accurate determination of low-frequency modes is essential to infer the structure of the solar core by inversion of the mode frequencies. In this paper we investigate how the changes in frequencies of low-degree modes obtained by fitting symmetric and asymmetric peak profiles change the inferred properties of the solar core. We use data obtained by the Global Oscillations at Low Frequencies (GOLF) project on board the SoHO spacecraft. Two different solar models and inversion procedures are used to invert the data to determine the sound speed in the solar core. We find that for a given set of modes no significant difference in the inferred sound-speed results from taking asymmetry into account when fitting the low-degree modes.

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Asymmetries of solar oscillation line profiles

Cited by 151 publications

References 0 publications

Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

On the Variation of the Peak Asymmetry of Low‐ℓ SolarpModes

Structure of the Solar Core: Effect of Asymmetry of Peak Profiles

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