伽玛暴(Gamma-Ray Burst)笔记。记录有关伽玛暴的新文章,另外也包括看的老文章、自己的想法、以及跟天文相关的一些东西。 Feel free to leave me a message by comments or by email.

星期四, 九月 13, 2007

Mizuno 2007 磁流体力学驱动相对论喷流

主要内容:
虽然伽玛暴还有很多其它现象要求极端相对论性的喷流,但是目前还没有可靠的模型来产生这种喷流。文章采用别人的程序,考虑磁流体力学,数值模拟出了极端相对论性的喷流。

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文章信息:

arXiv:0709.1839 [ps, pdf, other]
Title: A Magnetohydrodynamic Boost for Relativistic Jets
Authors: Yosuke Mizuno (NSSTC/NASA-MSFC), Philip Hardee (UA), Dieter H. Hartmann (Clemson Univ.), Ken-Ichi Nishikawa (NSSTC/UAH), Bing Zhang (UNLV)
Comments: 25 pages, 10 figures, accepted for publication in ApJ
Subjects: Astrophysics (astro-ph)

We performed relativistic magnetohydrodynamic simulations of the hydrodynamic boosting mechanism for relativistic jets explored by Aloy & Rezzolla (2006) using the RAISHIN code. Simulation results show that the presence of a magnetic field changes the properties of the shock interface between the tenuous, overpressured jet ($V^z_j$) flowing tangentially to a dense external medium. Magnetic fields can lead to more efficient acceleration of the jet, in comparison to the pure-hydrodynamic case. A ``poloidal'' magnetic field ($B^z$), tangent to the interface and parallel to the jet flow, produces both a stronger outward moving shock and a stronger inward moving rarefaction wave. This leads to a large velocity component normal to the interface in addition to acceleration tangent to the interface, and the jet is thus accelerated to larger Lorentz factors than those obtained in the pure-hydrodynamic case. Likewise, a strong ``toroidal'' magnetic field ($B^y$), tangent to the interface but perpendicular to the jet flow, also leads to stronger acceleration tangent to the shock interface relative to the pure-hydrodynamic case. Overall, the acceleration efficiency in the ``poloidal'' case is less than that of the ``toroidal'' case but both geometries still result in higher Lorentz factors than the pure-hydrodynamic case. Thus, the presence and relative orientation of a magnetic field in relativistic jets can significant modify the hydrodynamic boost mechanism studied by Aloy & Rezzolla (2006).

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