Hostname: page-component-cd9895bd7-gbm5v Total loading time: 0 Render date: 2024-12-25T16:58:12.665Z Has data issue: false hasContentIssue false
  • English
  • Français

Magnetohydrostatic equilibrium in starspots: dependences on color (Teff) and surface gravity (g)

Published online by Cambridge University Press:  26 August 2011

S. P. Rajaguru  and
S. S. Hasan
S. P. Rajaguru
Affiliation:
Indian Institute of Astrophysics, Bangalore - 560034, India, email: [email protected]
S. S. Hasan
Affiliation:
Indian Institute of Astrophysics, Bangalore - 560034, India, email: [email protected]
Rights & Permissions [Opens in a new window]

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.

Temperature contrasts and magnetic field strengths of sunspot umbrae broadly follow the thermal-magnetic relationship obtained from magnetohydrostatic equilibrium. Using a compilation of recent observations, especially in molecular bands, of temperature contrasts of starspots in cool stars, and a grid of Kurucz stellar model atmospheres constructed to cover layers of sub-surface convection zone, we examine how the above relationship scales with effective temperature (Teff), surface gravity g and the associated changes in opacity of stellar photospheric gas. We calculate expected field strengths in starpots and find that a given relative reduction in temperatures (or the same darkness contrasts) yield increasing field strengths against decreasing Teff due to a combination of pressure and opacity variations against Teff.

Keywords

Sun: magnetic fieldssunspotsstars: magnetic fieldsstars: spotsstars: activity
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S273: The Physics of Sun and Star Spots , August 2010 , pp. 276 - 280
Copyright
Copyright © International Astronomical Union 2011

References

Alexander, D. R. & Ferguson, J. W. 1994, ApJ, 437, 879CrossRefGoogle Scholar
Berdyugina, S. 2005, Living Rev. Solar Phys., 2, 8; URL: www.livingreviews.org/lrsp-2008-8CrossRefGoogle Scholar
Cox, J. P. & Giuli, R. T. 1968, Principles of Stellar Structure, Vol. 2, New York: Gordon & Breach, p590Google Scholar
Kurucz, R. L. 1993, ATLAS9 Stellar Atmosphere Programs and 2 km/s grid, Kurucz CD-ROM No.13. Cambridge, Mass.: Smithsonian Astrophysical Observatory.Google Scholar
Kurucz, R. L. 2001, private communicationGoogle Scholar
Lockwood, G. W., Skiff, B. A., Baliunas, S. L., & Radick, R. R. 1992, Nature, 360, 653CrossRefGoogle Scholar
Maltby, P. 1977, Solar Phys., 57, 335CrossRefGoogle Scholar
O'Neal, D., Saar, S. H., & Neff, J. E. 1996, ApJ, 463, 766CrossRefGoogle Scholar
Rajaguru, S. P., Kurucz, R. L., & Hasan, S. S. 2002, ApJ, 565, L101CrossRefGoogle Scholar
Saar, S. H. 1990, in IAU Symposium No. 138 Solar Photosphere: Structure, Convection, and Magnetic Fields, ed. Stenflo, J. O. (Kluwer: Dordrecht), p427CrossRefGoogle Scholar
Solanki, S. K., Walther, U., & Livingston, W. 1993, A&A, 277, 639Google Scholar