Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/3545
Title: Magnetoatmospheric oscillations in sunspot umbrae
Authors: Hasan, S. S
Keywords: Solar atmosphere;Solar magnetic field;Solar oscillations;Sunspots;Atmospheric models;Kinetic energy;Linear equations;Magnetic field configurations;Photosphere;Solar temperature
Issue Date: Jan-1990
Publisher: The American Astronomical Society
Citation: Astrophysical Journal, Part 1 , Vol. 366, No. 1, pp. 328 - 339
Abstract: The nature of umbral oscillations is investigated using an empirical model for the sunspot umbra, based on the model of Maltby et al. (1986). Approximating the sunspot as a thick flux tube of circular cross section, the axisymmetric normal modes of magnetoatmospheric waves were determined, and a diagnostic diagram was generated for different field strengths. The diagram shows the existence of 'avoided crossings' in the solution of magnetoatmospheric modes in a sunspot atmosphere. It was found that, for low values of the radial wavenumber k, corresponding to observed oscillations, a simple global classification is not possible. The oscillations in the low photosphere and below are of either fast or mixed type, but tend to acquire a slow or acoustic character above the temperature minimum.
URI: http://hdl.handle.net/2248/3545
ISSN: 0004-637X
???metadata.dc.relation.uri???: http://dx.doi.org/10.1086/169566
Appears in Collections:IIAP Publications

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