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Classification of Magnetoatmospheric Modes in Sunspot Umbrae

Published online by Cambridge University Press:  08 February 2017

S.S. Hasan  and
Y. Sobouti
S.S. Hasan
Affiliation:
Indian Institute of Astrophysics Bangalore 560034, India
Y. Sobouti
Affiliation:
Physics Department Shiraz, Iran

Abstract

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We examine the wave modes in a sunspot umbra. Assuming a stratification, based on a model atmosphere in a sunspot, the normal mode spectrum is determined. The modes are classified using a scheme based on a Helmholtz decomposition of the displacements into l(longitudinal) and t(transverse) components. In certain cases these can be related to the usual fast and slow MHD waves. We compute the theoretical eigenfrequencies and note the existence of umbral oscillations with periods in the range 2-3 min, which are interpreted as slow and mixed modes. The frequencies of the Alfvén waves are also calculated. It is suggested that these modes might also have been observed.

Type
IV. Magnetohydrodynamics of the Photosphere
Information
Symposium - International Astronomical Union , Volume 138: Solar Photosphere: Structure, Convection and Magnetic Fields , 1990 , pp. 255 - 258
Copyright
Copyright © Kluwer 1990 

References

Abdelatif, T.E., Lites, B.W., and Thomas, J.H.(1986), Astrophys. J. 311, 1015.Google Scholar
Antia, H. and Chitre, S.M. (1979), Solar Phys. 63, 67.Google Scholar
Balthasar, H. and Wiehr, E. (1984), Solar Phys. 94, 99.Google Scholar
Balthasar, H., Küveler, G., and Wiehr, E. (1987), Solar Phys. 112, 39–48.Google Scholar
Beckers, J.M. and Schulz, R.B. (1972), Solar Phys. 27, 61.Google Scholar
Bhatnagar, A., Livingston, W.C., and Harvey, J.W. (1972), Solar Phys. 27, 80.Google Scholar
Gurman, J.B. and Leibacher, J.W. (1984), Astrophys. J. 283, 859.Google Scholar
Gurman, J.B. (1987), Solar Phys. 108, 61.Google Scholar
Hasan, S.S. and Sobouti, Y. (1987), Mon. Not. R. astr. Soc. 228, 427.Google Scholar
Leroy, B. and Schwartz, S.J. (1982), Astron. Astrophys. 112, 84.Google Scholar
Lites, B.W. and Thomas, J.H. (1985), Astrophys. J. 294, 682.CrossRefGoogle Scholar
Lites, B.W. (1986), Astrophys. J. 301, 922.Google Scholar
Maltby, P., Avrett, E.H., Carlsson, M., Kjeldseth-Moe, O., Kurucz, R.L. and Loeser, R. (1986), Astrophys. J. 306, 284.Google Scholar
Scheuer, M.A. and Thomas, J.H. (1981), Solar Phys. 71, 21.CrossRefGoogle Scholar
Schröter, E.H. and Soltau, D. (1976), Astron. Astrophys. 449, 463.Google Scholar
Sobouti, Y. (1981), Astron. Astrophys. 100, 319.Google Scholar
Soltau, D., Schröter, E.H., and Wöhl, H. (1976), Astron. Astrophys. 50, 367.Google Scholar
Thomas, J.H., Lites, B.W., and Gurman, J.B. (1987), Astrophys. J. 312,457.Google Scholar
Uchida, Y. and Sakurai, T. (1975), Publ. Astron. Soc. Japan 27, 259.Google Scholar
Zhugzhda, Y.D. (1979), Sov. Astron. 23, 42.Google Scholar
Zhugzhda, Y.D., Locan, V., and Staude, J. (1983) Solar Phys. 82, 369.Google Scholar