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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 |
Appears in Collections: | IIAP Publications |
Files in This Item:
File | Description | Size | Format | |
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Magnetoatmospheric oscillations in sunspot umbrae | 1.97 MB | Adobe PDF | View/Open |
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