Classification of Magnetoatmospheric Modes in Sunspot Umbrae

dc.contributor.author	Hasan, S. S
dc.contributor.author	Sobouti, Y
dc.date.accessioned	2008-09-10T12:28:11Z
dc.date.available	2008-09-10T12:28:11Z
dc.date.issued	1990
dc.identifier.citation	IAU Symposium, No. 138, pp. 255 - 258	en
dc.identifier.issn	0074-1809
dc.identifier.uri	http://hdl.handle.net/2248/3529
dc.description.abstract	We examine the wave modes in a sunspot umbra. Assuming 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 displacement in to 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 of 2-3 min, which are interpreted as slow and mixed modes. The frequencies of the Alfven waves are also calculated. It is suggested that these modes might also have been observed.	en
dc.language.iso	en	en
dc.publisher	International Astronomical Union	en
dc.relation.uri	http://adsabs.harvard.edu/abs/1990IAUS..138..255H	en
dc.subject	Magnetospheric modes	en
dc.subject	Solar Photosphere: Structure	en
dc.subject	Magnetic Fields	en
dc.title	Classification of Magnetoatmospheric Modes in Sunspot Umbrae	en
dc.type	Article	en