Solar interior structure and luminosity variations
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The assumptions of standard solar evolution theory are mentioned briefly, and the principle conclusions drawn from them are described. The result is a rationalization of the present luminosity and radius of the Sun. Because there is some uncertainty about the interior composition of the Sun, a range of models is apparently acceptable.
To decide which model is the most accurate, other more sensitive comparisons with observations must be made. Recent measurements of frequencies of dynamical oscillations are particularly valuable in this respect. The most accurate observations are of the five-minute oscillations, which suggest that the solar composition is not atypical of other stars of the same age as the Sun.
The theory predicts that the solar luminosity has risen steadily from about 70% of its current value during the last 4.7 x 109yr. Superposed on this there might have been variations on shorter timescales. Variations lasting about 107yr and occurring at intervals of 108yr have been suggested as being the cause of terrestrial ice ages. Moreover, there may be other variations, associated with instabilities arising from the coupling between the convection zone and the radiative interior, that occur on a timescale of 105yr and which also have climatic consequences. These issues are quite uncertain.
We do know that the Sun varies magnetically with a period of about 22 yr, and that this oscillation is modulated irregularly on a timescale of centuries. This appears to be a phenomenon associated with the convection zone and its immediate neighbourhood, though control from a more deeply-seated mechanism is not out of the question. There is a small luminosity variation associated with this cycle, and the way by which this might come about is discussed in terms of certain theories of the solar dynamo.
Finally, there must be small surface flux variations associated with the dynamical oscillations mentioned above. Though the total luminosity variations are extremely small, the flux in any specific direction, and in particular that of the earth, may be measurable.
KeywordsSurface Flux Convection Zone Flux Variation Short Timescale Interior Structure
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- Bahcall, J. N.: 1979, Space Sci. Rev. 24, 227.Google Scholar
- Bahcall, J. N., Huebner, W. F., Lubow, S. H., Magee Jr, N. H., Merts, A. L., Parker, P. D., Rozsnya, B., Ulrich, R. K., and Argo, M. F.: 1980, Phys. Rev. Letters 45, 945.Google Scholar
- Barnes, J. A., Sargent III, H. H., and Tyron, P. V.: 1980, in J. A. Eddy, R. O. Pepin, and R. B. Merrill (eds.), Proc. Conference on the Ancient Sun, Pergamon, London, p. 159.Google Scholar
- Bell, P. R.: 1981, in S. Sofia (ed.), Proc. Workshop on Solar Constant Variations, NASA, Greenbelt, in press.Google Scholar
- Berthomieu, G., Cooper, A. J., Gough, D. O., Osaki, Y., Provost, J., and Rocca, A.: 1980, in H. A. Hill and W. A. Dziembowski (eds.), Nonradial and Nonlinear Stellar Pulsation, Springer, Heidelberg, p. 307.Google Scholar
- Christensen-Dalgaard, J. and Gough, D. O.: 1980, Nature 288, 544.Google Scholar
- Claverie, A., Isaak, G. R., McLeod, C. P., van der Raay, H. B., and Roca-Cortes, T.: 1979, Nature 282, 591.Google Scholar
- Cowling, T. G.: 1953, in G. P. Kuiper (ed.), The Sun, University of Chicago Press, Chicago, p. 565.Google Scholar
- Davis Jr, R.: 1978, in G. Friedlander (ed.), Proc. Informal Conf, on Status and Future of Solar Neutrino Research, Brookhaven Nat. Lab. 50879, Upton Vol. 1, p. 1.Google Scholar
- Dearborn, D. S. P. and Blake, J. B.: 1980, Astrophys. J. 237, 616.Google Scholar
- Dearborn, D. S. P. and Newman, M. J.: 1978, Science 201, 150.Google Scholar
- Deubner, F.-L.: 1975, Astron. Astrophys. 44, 371.Google Scholar
- Deubner, F.-L., Ulrich, R. K., and Rhodes Jr, E. J.: 1979, Astron. Astrophys. 72, 177.Google Scholar
- Dicke, R. H.: 1978, Nature 276, 676.Google Scholar
- Dicke, R. H.: 1979a, New Scientist 83, 12.Google Scholar
- Dicke, R. H.: 1979b, Nature 280, 24.Google Scholar
- Drobyshevski, E. M. and Yuferev, V. S.: 1974, J. Fluid Mech. 65, 33.Google Scholar
- Eddy, J. A. and Boornazian, A. A.: 1979, Bull. Am. Astron. Soc. 11, 437.Google Scholar
- Epstein, S. and Yapp, C. J.: 1976, Earth Planet. Sci. Letters 30, 252.Google Scholar
- Fossat, E., Grec, G., and Pomerantz, M.: 1981, Solar Phys. 74, 59 (this volume).Google Scholar
- Gough, D. O.: 1978, in J. Rösch (ed.), Pleins feux sur la physique solaire, CNRS, Paris, p. 81.Google Scholar
- Gough, D. O.: 1980, in H. A. Hill and W. A. Dziembowski (eds.), Nonradial and Nonlinear Stellar Pulsation, Springer, Heidelberg, p. 273.Google Scholar
- Gough, D. O.: 1981, in S. Sofia (ed.), Proc. Workshop on Solar Constant Variations, NASA, Greenbelt, in press.Google Scholar
- Grec, G., Fossat, E., and Pomerantz, M.: 1980, Nature 288, 541.Google Scholar
- Joss, P. C.: 1974, Astrophys. J. 191, 771.Google Scholar
- Lubow, S., Rhodes, Jr, E. J., and Ulrich, R. K.: 1980, in H. A. Hill and W. A. Dziembowski (eds.), Nonradial and Nonlinear Stellar Pulsation, Springer, Heidelberg, p. 300.Google Scholar
- Mitchell Jr, J. M., Stockton, C. W., and Meko, D. M.: 1979, in B. M. McCormac and T. A. Seliga, (eds.), Solar-Terrestrial Influences on Weather and Climate, D. Reidel Publ. Co., Dordrecht, Holland, p. 125.Google Scholar
- Newkirk Jr, G.: 1980, J. A. Eddy, R. O. Pepin, and R. B. Merrill (eds.), Proc. Conference on the Ancient Sun, Pergamon, London, p. 293.Google Scholar
- Parker, E. N.: 1979, Cosmical Magnetic Fields, Clarendon, Oxford.Google Scholar
- Reines, F., Sobel, H., and Pasier, B. E.: 1980, Phys. Rev. Letters, 45, 1307.Google Scholar
- Ross, J. E. and Aller, L. H.: 1976, Science 191, 1223.Google Scholar
- Rosenwald, R. D. and Hill, H. A.: 1980, in H. A. Hill and W. A. Dziembowski (eds.), Nonradial and Nonlinear Stellar Pulsation, Springer, Heidelberg, p. 404.Google Scholar
- Shapiro, I. I.: 1980, Science 208, 51.Google Scholar
- Sofia, S., O'Keefe, J., and Lesh, J. R.: 1979, Science 204, 1306.Google Scholar
- Sofia, S., Dunham, D. W., and Fiala, A. D.: 1980, in J. A. Eddy, R. O. Pepin, and R. B. Merrill (eds.), Proc. Conference on the Ancient Sun, Pergamon, London, p. 147.Google Scholar
- Spiegel, E. A. and Weiss, N. O.: 1980, Nature 287, 616.Google Scholar
- Stix, M.: 1981, Solar Phys. 74, 79 (this volume).Google Scholar
- Waldmeier, M.: 1961, The Sunspot-Activity in the Years 1610–1960, Schulthess, Zürich.Google Scholar
- Weiss, N. O. 1966, Proc. Roy. Soc. A293, 310.Google Scholar
- Wittmann, A.: 1980, Solar Phys. 66, 223.Google Scholar