Changes in convective properties over the solar cycle: effect on p-mode damping rates

HOUDEK, G., CHAPLIN, W. J., APPOURCHAUX, T., CHRISTENSEN-DALSGAARD, J., DAPPEN, W., ELSWORTH, Y., GOUGH, D. O., ISAAK, G. R., NEW, R. and RABELLO-SOARES, M. C. (2001). Changes in convective properties over the solar cycle: effect on p-mode damping rates. Monthly notices of the Royal Astronomical Society, 327 (2), 483-487.

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Measurements of both solar irradiance and p-mode oscillation frequencies indicate that the structure of the Sun changes with the solar cycle. Balmforth, Gough & Merryfield investigated the effect of symmetrical thermal disturbances on the solar structure and the resulting pulsation frequency changes. They concluded that thermal perturbations alone cannot account for the variations in both irradiance and p-mode frequencies, and that the presence of a magnetic field affecting acoustical propagation is the most likely explanation of the frequency change, in the manner suggested earlier by Gough & Thompson and by Goldreich et al. Numerical simulations of Boussinesq convection in a magnetic field have shown that at high Rayleigh number the magnetic field can modify the preferred horizontal length scale of the convective flow. Here, we investigate the effect of changing the horizontal length scale of convective eddies on the linewidths of the acoustic resonant mode peaks observed in helioseismic power spectra. The turbulent fluxes in these model computations are obtained from a time-dependent, non-local generalization of the mixing-length formalism. The modelled variations are compared with p-mode linewidth changes revealed by the analysis of helioseismic data collected by the Birmingham Solar-Oscillations Network (BiSON); these low-degree (low-l) observations cover the complete falling phase of solar activity cycle 22. The results are also discussed in the light of observations of solar-cycle variations of the horizontal size of granules and with results from 2D simulations by Steffen of convective granules.

Item Type: Article
Research Institute, Centre or Group - Does NOT include content added after October 2018: Materials and Engineering Research Institute > Advanced Coatings and Composites Research Centre > Nanotechnology Centre for PVD Research
Identification Number:
Page Range: 483-487
Depositing User: Ann Betterton
Date Deposited: 19 May 2010 16:46
Last Modified: 18 Mar 2021 09:30

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