Open AccessElastic or magnetic? A toy model for global magnetar oscillations with implications for quasi‐periodic oscillations during flares
Author(s) -
Glampedakis Kostas,
Samuelsson Lars,
Andersson Nils
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2006.00211.x
Subject(s) - magnetar , physics , flare , crust , neutron star , coupling (piping) , magnetohydrodynamic drive , astrophysics , magnetohydrodynamics , magnetic field , geophysics , quantum mechanics , mechanical engineering , engineering
We use a simple toy‐model to discuss global magnetohydrodynamic modes of a neutron star, taking into account the magnetic coupling between the elastic crust and the fluid core. Our results suggest that the notion of pure torsional crust modes is not useful for the coupled system. All modes excite Alfvén waves in the core. However, we also show that the modes that are most likely to be excited by a fractured crust, e.g. during a magnetar flare, are such that the crust and the core oscillate in concert. For our simple model, the frequencies of these modes are similar to the ‘pure crustal’ frequencies. In addition, our model provides a natural explanation for the presence of lower frequency (<30 Hz) quasi‐periodic oscillations seen in the 2004 December giant flare of SGR 1806−20.