期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 456, 期 2, 页码 1739-1760出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stv2591
关键词
gamma-ray burst: general; stars: magnetars; stars: magnetic field; galaxies: jets; quasars: general
资金
- Lyman Spitzer Jr Fellowship - Department of Astrophysical Sciences at Princeton University
- Max-Planck/Princeton Center for Plasma Physics
- NASA - Chandra X-ray Center [PF3-140115]
- NASA [NAS8-03060]
- Direct For Mathematical & Physical Scien
- Division Of Physics [1144374, 1410972, 1523261] Funding Source: National Science Foundation
Relativistic jets are associated with extreme astrophysical phenomena, like the core collapse of massive stars in gamma-ray bursts (GRBs) and the accretion on to supermassive black holes in active galactic nuclei. It is generally accepted that these jets are powered electromagnetically, by the magnetized rotation of a central compact object (black hole or neutron star). However, how the jets produce the observed emission and survive the propagation for many orders of magnitude in distance without being disrupted by current-driven instabilities is the subject of active debate. We carry out time-dependent 3D relativistic magnetohydrodynamic (MHD) simulations of relativistic, Poynting-flux-dominated jets. The jets are launched self-consistently by the rotation of a strongly magnetized central object. This determines the natural degree of azimuthal magnetic field winding, a crucial factor that controls jet stability. We find that the jets are susceptible to two types of instability: (i) a global, external kink mode that grows on long time-scales. It bodily twists the jet, reducing its propagation velocity. We show analytically that in flat density profiles, like the ones associated with galactic cores, the external mode grows and may stall the jet. In the steep profiles of stellar envelopes the external kink weakens as the jet propagates outward. (ii) a local, internal kink mode that grows over short time-scales and causes small-angle magnetic reconnection and conversion of about half of the jet electromagnetic energy flux into heat. We suggest that internal kink instability is the main dissipation mechanism responsible for powering GRB prompt emission.
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