Hostname: page-component-586b7cd67f-dlnhk Total loading time: 0 Render date: 2024-11-28T10:56:12.545Z Has data issue: false hasContentIssue false
  • English
  • Français

Convection and Irradiance Variations

Published online by Cambridge University Press:  12 April 2016

Peter A. Fox  and
Sabatino Sofia
Peter A. Fox
Affiliation:
High Altitude Observatory, National Center for Atmospheric Research, Boulder CO 80307, USA
Sabatino Sofia
Affiliation:
Center for Solar and Space Research, Yale University New Haven, CT 06511, USA

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

In the outer layers of the Sun (≈ 30% by radius), energy is transported by convection. The nature of the highly stratified and compressible convective flow is determined from the components of the energy flux (internal, kinetic, viscous, magnetic and radiative). Local suppressions or enhancements of any of these components may give rise to measurable changes in the emergent radiation.

On the solar surface there is direct evidence for modulation of the emerging heat flux covering a large range in spatial and temporal scales, particularly associated with concentrated magnetic fields (e.g. sunspots, plages). Associated with these surface features is the observation that the characteristics of convective motions are also modified. In the deeper layers, the interaction of convection and magnetic fields will play an important role in readjusting the local emerging heat flux and thus should contribute to the modulation of the total solar irradiance.

The task of calculating the response of the convection zone structure to developing active regions, and the solar activity cycle in general is difficult and complex due to the highly non-linear nature of the interaction of convection and magnetic fields. Theoretical work has ranged from empirical and global structure models, all the way to fine scale compressible convection simulations. This paper will highlight some recent theoretical advances that may have a direct bearing on the understanding of solar luminosity and irradiance variations and outline the important problems that must be addressed and what observational constraints may be used.

Type
Solar and Stellar Oscillations, Irradiance Variations, and their Interpretation
Information
International Astronomical Union Colloquium , Volume 143: The Sun as a Variable Star: Solar and Stellar Irradiance Variations , 1994 , pp. 280 - 290
Copyright
Copyright © Kluwer 1994

References

Chan, K.L. & Sofia, S. 1986 Turbulent compressible convection in a deep atmosphere III: tests on the validity and limitations of the numerical approach. Astrophys. J. 307, 222–241.Google Scholar
Chan, K.L. & Sofia, S. 1989 Turbulent compressible convection in a deep atmosphere IV: results of three-dimensional computations. Astrophys. J. 336, 1022–1040.Google Scholar
Cattaneo, F., Brummell, N.H., Toomre, J., Malagou, A. & Hurlburt, N.E. 1991 Turbulent compressible convection. Astrophys. J. 370, 282–294.Google Scholar
Chiang, W.H. & Foukal, P. 1984 The influence of faculae on sunspot heat blocking. Solar Phys. 97, 9–20.Google Scholar
Endal, A.S., Sofia, S. & Twigg, L. 1985 Changes in solar luminosity and radius following secular perturbations in the convective envelope. Astrophys. J. 290, 748–757.Google Scholar
Foukal, P., Fowler, L.A. & Livshits, M. 1983 A thermal model of sunspot influence on solar luminosity. Astrophys. J. 267, 863–871.Google Scholar
Fowler, L.A., Foukal, P. & Duvall, T. 1983 Sunspot bright rings and the thermal diffusivity of solar convection. Solar Phys. 84, 33–44.Google Scholar
Fox, P.A., Sofia, S. & Chan, K.L. 1991 Convective flows around sunspot-like objects. Solar Phys. 135, 15–42.Google Scholar
Fox, P.A., Theobald, M.L. & Sofia, S. 1991 Compressible magnetic convection: formulation and two-dimensional models. Astrophys. J. 383, 860–881.Google Scholar
Friis-Christenen, E. & Lassen, K. 1991 Length of the solar cycle: an indicator of solar activity closely associated with climate. Science 254, 698–700.Google Scholar
Kuhn, J.R. 1989 Helioseismic observations of the solar cycle. Astrophys. J. 339, L45–L47.Google Scholar
Kuhn, J.R. 1991 Inferring solar structure variations from photometric and helioseismic observations., preprint.Google Scholar
Livingston, W.C. 1990 Sun-as-a-star. its convective signature and the activity cycle.. In The Sun and Cool Stars: Activity, Magnetism and Dynamos (ed. Tuominen, I., Moss, D. &: Rüdiger, G.). Lecture Notes in Physics, vol. 380, pp. 246–251. Spring-Verlarg.Google Scholar
Lydon, T.J., Fox, P.A. & Sofia, S. 1992 A formulation of convection for stellar structure and evolution calculations without the MLT approximations I. application to the Sun. Astrophys. J. 397, 701–716.Google Scholar
Lydon, T.J., Fox, P.A. & Sofia, S. 1993a Improved solar models constructed with a formulation of convection for stellar structure and evolution calculations without the MLT approximations. Astrophys. J. 403, L79–L82.Google Scholar
Lydon, T.J., Fox, P.A. & Sofia, S. 1993b A formulation of convection for stellar structure and evolution calculations without the MLT approximations II. application to α Centauri A and B. Astrophys. J. 413, 390–400.Google Scholar
McIntosh, P.S. 1994, in preparation.Google Scholar
Nye, A., Bruning, D. & Labonte, B.J. 1988 Mass and energy flow near sunspots: II. Linear numerical models of moat flow. Solar Phys. 115, 251–268.Google Scholar
Spruit, H.-C. 1976 Pressure equilibrium and energy balance of small photospheric flux tubes. Solar Phys. 50, 269–295.Google Scholar
Spruit, H.-C. 1977 Heat flow near obstacles in the solar convection zone. Solar Phys. 55, 3–34.Google Scholar
Stein, R.F. & Nordlund, A. 1989 Toplogy of convection beneath the solar surface. Astrophys. J. 342, L95–L98.Google Scholar
White, O.R. 1994 The solar spectral irradiances from X-ray to radio wavelengths. In The Sun as a Variable Star: Solar and Stellar Irradiance Variations (ed. Pap, J.M., Fröhlich, C., Hudson, H.S. & Solanki, S.K.). Cambridge University Press, in press.Google Scholar
Vitense, E. 1953 Die Wasserstoffkonvektionszone. Z.F. Astrophys. 32, 135–164.Google Scholar