dc.contributor.author |
Hasan, S. S |
|
dc.date.accessioned |
2008-09-11T15:53:48Z |
|
dc.date.available |
2008-09-11T15:53:48Z |
|
dc.date.issued |
1990-01 |
|
dc.identifier.citation |
Astrophysical Journal, Part 1 , Vol. 366, No. 1, pp. 328 - 339 |
en |
dc.identifier.issn |
0004-637X |
|
dc.identifier.uri |
http://hdl.handle.net/2248/3545 |
|
dc.description.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. |
en |
dc.language.iso |
en |
en |
dc.publisher |
The American Astronomical Society |
en |
dc.relation.uri |
http://dx.doi.org/10.1086/169566 |
en |
dc.subject |
Solar atmosphere |
en |
dc.subject |
Solar magnetic field |
en |
dc.subject |
Solar oscillations |
en |
dc.subject |
Sunspots |
en |
dc.subject |
Atmospheric models |
en |
dc.subject |
Kinetic energy |
en |
dc.subject |
Linear equations |
en |
dc.subject |
Magnetic field configurations |
en |
dc.subject |
Photosphere |
en |
dc.subject |
Solar temperature |
en |
dc.title |
Magnetoatmospheric oscillations in sunspot umbrae |
en |
dc.type |
Article |
en |