Solar Physics

, Volume 141, Issue 2, pp 235–251 | Cite as

Magnetoacoustic-gravity surface waves

II. Uniform Magnetic Field
  • Alan J. Miles
  • H. R. Allen
  • B. Roberts
Article

Abstract

The linearized theory for the parallel propagation of magnetoacoustic-gravity surface waves is developed and a dispersion relation obtained for the case of an isothermal interface of a uniform horizontal magnetic field residing above a field-free medium. The transcendental dispersion relation is solved numerically for a range of parameters and the resulting dispersion curves and corresponding eigenfunctions plotted. As in the case of a uniform Alfvén speed (Paper I), the existence of the fast and slow magnetoacoustic-gravity surface modes and the f-mode (modified by the presence of the uniform magnetic field) is determined by the relative temperatures of the two media either side of the interface. If the lower field-free region is cooler than the upper magnetic atmosphere only the slow magnetoacoustic-gravity surface mode may propagate. In addition to these three surface modes we find higher harmonic-type trapped modes. The existence of these modes also depends on the temperatures either side of the interface. They propagate only when both the field-free region is warmer than the magnetic field region and the Alfvén speed is greater than the corresponding sound speed in the magnetic atmosphere.

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References

  1. Abramowitz, M. and Stegun, I. A.: 1965, Handbook of Mathematical Functions, Dover Publ., New York.Google Scholar
  2. Adam, J. A.: 1975, Ph.D. Thesis, University of London.Google Scholar
  3. Adam, J. A.: 1977, Solar Phys. 52, 293.Google Scholar
  4. Evans, D. J. and Roberts, B.: 1990, Astrophys. J. 356, 704.Google Scholar
  5. Goedbloed, J. P.: 1971, Physica 53, 412.Google Scholar
  6. González, A. G. and Gratton, J.: 1991, Solar Phys. 134, 211.Google Scholar
  7. Kumar, P., Duvall, T. L., Jr., Harvey, J. W., Jefferies, S. M., Pomerantz, M. A., and Thompson, M. J.: 1991, Lecture Notes in Physics 367, 87.Google Scholar
  8. Lamb, H.: 1932, Hydrodynamics, Cambridge University Press, Cambridge, Chapter X.Google Scholar
  9. Miles, A. J. and Roberts, B.: 1989, Solar Phys. 119, 257.Google Scholar
  10. Miles, A. J. and Roberts, B.: 1991, in M. Dubois, F. Bely-Dubau, and D. Gresillon (eds.), Plasma Phenomena in the Solar Atmosphere, Cargèse, p. 77.Google Scholar
  11. Miles, A. J. and Roberts, B.: 1992, Solar Phys. 141, 205 (Paper I).Google Scholar
  12. Nye, A. H. and Thomas, J. H.: 1976a, Astrophys. J. 204, 573.Google Scholar
  13. Nye, A. H. and Thomas, J. H.: 1976b, Astrophys. J. 204, 582.Google Scholar
  14. Roberts, B.: 1981, Solar Phys. 69, 27.Google Scholar
  15. Roberts, B.: 1985, in E. R. Priest (ed.), Solar System Magnetic Fields, D. Reidel Publ. Co., Dordrecht, Holland, p. 37.Google Scholar
  16. Small, L. M. and Roberts, B.: 1984, in The Hydromagnetics of the Sun, ESA SP-220, p. 257.Google Scholar
  17. Wentzel, D. G.: 1979, Astrophys. J. 227, 319.Google Scholar
  18. Woodard, M. F. and Libbrecht, K. G.: 1991, Astrophys. J. 374, L61.Google Scholar

Copyright information

© Kluwer Academic Publishers 1992

Authors and Affiliations

  • Alan J. Miles
    • 1
  • H. R. Allen
    • 1
  • B. Roberts
    • 1
  1. 1.Department of Mathematical and Computational SciencesUniversity of St. AndrewsSt. Andrews, FifeScotland

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