NDLI: Transverse kink oscillations in the presence of twist

Content Provider	EDP Sciences
Author	J. Terradas M. Goossens
Abstract	Context. Magnetic twist is thought to play an important role in coronal loops. The effects of magnetic twist on stable magnetohydrodynamic (MHD) waves is poorly understood because they are seldom studied for relevant cases.Aims. The goal of this work is to study the fingerprints of magnetic twist on stable transverse kink oscillations.Methods. We numerically calculated the eigenmodes of propagating and standing MHD waves for a model of a loop with magnetic twist. The azimuthal component of the magnetic field was assumed to be small in comparison to the longitudinal component. We did not consider resonantly damped modes or kink instabilities in our analysis.Results. For a nonconstant twist the frequencies of the MHD wave modes are split, which has important consequences for standing waves. This is different from the degenerated situation for equilibrium models with constant twist, which are characterised by an azimuthal component of the magnetic field that linearly increases with the radial coordinate. Conclusions. In the presence of twist standing kink solutions are characterised by a change in polarisation of the transverse displacement along the tube. For weak twist, and in the thin tube approximation, the frequency of standing modes is unaltered and the tube oscillates at the kink speed of the corresponding straight tube. The change in polarisation is linearly proportional to the degree of twist. This has implications with regard to observations of kink modes, since the detection of this variation in polarisation can be used as an indirect method to estimate the twist in oscillating loops.
Page Count	9
File Format	HTM / HTML PDF
ISSN	00046361
Alternate Webpage(s)	https://www.aanda.org/articles/aa/abs/2012/12/aa19934-12/aa19934-12.html
e-ISSN	14320746
Journal	Astronomy & Astrophysics
Volume Number	548
DOI	10.1051/0004-6361/201219934
Language	English
Publisher	EDP Sciences
Publisher Date	2012-12-01
Access Restriction	Open
Rights Holder	© ESO, 2012
Subject Keyword	magnetohydrodynamics (MHD) waves Sun: corona magnetohydrodynamics (MHD) / waves / Sun: corona
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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