Solar Physics: From the Deep Interior to the Hot Corona
We present an overview of the thermal properties of the Sun from the hot interior to the hot corona. For pedagogical reasons, we confine the discussion to certain relevant solutions of the energy conservation equation. In the interior, quantitative information can be obtained by using a polytropic equation of state: internal temperatures obtained in this way are found to be reliable to about 10%, and we can obtain a good estimate of the depth of the convection zone. In the chromosphere, acoustic waves originating in the convection zone do work on the gas: as the gas heats up, the atomic energy levels of many elements (especially hydrogen) exert a strong thermostatic control so that the temperature is confined to a steady value in the range 5000-104 K. In long-lived coronal loops, a steady state balance between thermal conduction and radiative losses causes the temperature of the electrons to lie in the range (1-2) million K. Coronal ions are heated to greater temperatures than electrons. In flares, processes of heating and cooling are explicitly non-steady, and short-lived excursions to temperatures as high as 25 million K (or more) are observed in the largest flares.
KeywordsSolar Wind Coronal Hole Solar Corona Solar Atmosphere Convection Zone
Unable to display preview. Download preview PDF.
- 1.J. Christensen-Dalsgaard: Solar model with helium diffusion and settling (1999) (JCD): available online at website http://helios.tuc.noao.edu/teams/models/gongwww.l4b.d.18.html
- 4.G. Isaak et al.: in Advances in Helio-and Asteroseismology, ed. by J. Christensen-Dalsgaard (Reidel, Dordrecht 1986) pp. 53–57Google Scholar
- 5.M. Schwarzschild: Structure and Evolution of the Stars, (Princeton Univ. Press 1958)Google Scholar
- 6.F. W. Sears: Thermodynamics, 2nd edn. (Addison Wesley, Reading MA 1959), pp. 267–269Google Scholar
- 7.R. Kurucz: Rosseland mean opacities for solar composition (1992): available online at website http://cfaku5.harvard.edu/OPACITIES/ROSSELAND/kapp00.ross
- 10.P. Foukal: Solar Astrophysics, (Wiley Interscience, New York 1990), p. 116Google Scholar
- 15.L. Biermann and R. Lust: in Stellar Atmospheres ed. by J. L. Greenstein (Univ. of Chicago Press, Chicago 1960) p. 272Google Scholar
- 17.L. Spitzer: Physics of Fully Ionized Gases, (Interscience, New York 1962), p. 128Google Scholar
- 27.D. S. Spicer and J. C. Brown: in The Sun as a Star ed. by S. Jordan (NASA SP-450 1982), pp. 413–471Google Scholar
- 28.D. S. Spicer: in: Activity in Red Dwarf Stars ed. by P. B. Byrne and M. Rodono (Reidel, Dordrecht 1982), p. 560Google Scholar