Journal Article

Relativistic expansion of magnetic loops at the self-similar stage

Hiroyuki R. Takahashi, Eiji Asano and Ryoji Matsumoto

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 394, issue 1, pages 547-568
Published in print March 2009 | ISSN: 0035-8711
Published online March 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.14357.x
Relativistic expansion of magnetic loops at the self-similar stage

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We obtained self-similar solutions of relativistically expanding magnetic loops taking into account the azimuthal magnetic fields. We neglect stellar rotation and assume axisymmetry and a purely radial flow. As the magnetic loops expand, the initial dipole magnetic field is stretched into the radial direction. When the expansion speed approaches the light speed, the displacement current reduces the toroidal current and modifies the distribution of the plasma lifted up from the central star. Since these self-similar solutions describe the free expansion of the magnetic loops, i.e. dv/dt= 0, the equations of motion are similar to those of the static relativistic magnetohydrodynamics. This allows us to estimate the total energy stored in the magnetic loops by applying the virial theorem. This energy is comparable to that of the giant flares observed in magnetars.

Keywords: MHD; relativity; stars: magnetic field; stars: neutron

Journal Article.  7821 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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