Are Quasar Jets Dominated by Poynting Flux?

By M. Sikora, M. Begelman, G. Madejski, Jan Lasota. 2005

133 citations recorded by the source corpus.

The formation of relativistic astrophysical jets is presumably mediated by magnetic fields threading accretion disks and central, rapidly rotating objects. As it is accelerated by magnetic stresses, the jet's kinetic energy flux grows at the expense of its Poynting flux. However, it is unclear how efficient the conversion from magnetic to kinetic energy is and whether there are any observational signatures of this process. We address this issue in the context of jets in quasars. Using data from all spatial scales, we demonstrate that in these objects the conversion from Poynting flux-dominated to matter-dominated jets is very likely to take place closer to the black hole than in the region where most of the Doppler-boosted radiation observed in blazars is produced. We briefly discuss the possibility that blazar activity could be induced by global MHD instabilities, e.g., via the production of localized velocity gradients that lead to dissipative events such as shocks or magnetic reconnection, in which acceleration of relativistic particles and production of nonthermal flares is taking place.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/00509daf26e50c0c183a09ada404ae8ec89cfb53

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Citations in the corpus

Radio Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications (2006, background): “The significant content of protons in quasar jets, as deduced from the analysis of blazar spectra (Sikora & Madejski 2000; Sikora et al. 2005), and indicated by the discovery of circular polarization in radio cores (Wardle et al. 1998; Homan et al. (2001).”
General relativistic magnetohydrodynamic simulations of the jet formation and large-scale propagation from black hole accretion systems (2006, background): “This is consistent with the lack of observed Comptonization features in blazars (see, e.g., Sikora et al. 2005).”
The power of blazar jets (2007, background): “…fields play a crucial role our results would require that magnetic acceleration must be rapid, since at the scale of a few hun- dreds Schwarzschild radii, where most of radiation is produce , the Poynting flux is no longer energetically dominant (confirming the results by Sikora et al. 2005).”
Magnetic acceleration of relativistic AGN jets (2007, methodology): “These properties of the extended magnetic acceleration region are in very good agreement with the observational inferences summarized in Section 1 (in particular, the lack of bulk-Comptonization spectral features in blazar jets; see Sikora et al. 2005).”
CONSTRAINING EMISSION MODELS OF LUMINOUS BLAZAR SOURCES (2009, background): “Such an apparent weakness of bulk-Compton features may result from the fact that in the very central regions of AGN jet the (magnetohydrodynamical, MDH) acceleration of the outflow is not yet fully complete (as noted previously in Sikora et al. 2005; Celotti et al. 2007).”
Dynamics and high-energy emission of the flaring HST-1 knot in the M 87 jet (2006, background): “On the other hand, a dominant electromagnetic jet flux should be converted at some point to the particle flux, since the large-scale jets seem to be rather particle dominated [see the discussion in Sikora et al. (2005)].”
MOJAVE. X. PARSEC-SCALE JET ORIENTATION VARIATIONS AND SUPERLUMINAL MOTION IN ACTIVE GALACTIC NUCLEI (2013, methodology): “While some models indicate that this process is largely complete with the conversion of Poynting flux to flow energy on sub-pc scales (e.g., Sikora et al. 2005), there may still be significant magnetic (Vlahakis & Königl 2004) or hydrodynamic acceleration which extends to parsec or decaparsec…”
PARTICLE ACCELERATION IN RELATIVISTIC MAGNETIZED COLLISIONLESS PAIR SHOCKS: DEPENDENCE OF SHOCK ACCELERATION ON MAGNETIC OBLIQUITY (2009, background): “Alternatively, particle acceleration may occur not in shocks but in reconnection layers of a Poynting-dominated jet, although Sikora et al. (2005) have shown that the jet is likely to be matter-dominated at the pc-scale emission region.”
The role of kink instability in Poynting-flux dominated jets (2006, background): “The case-dependent arguments are reviewed in Sikora et al. (2005), where it is shown that there is no strong observa- tional reason to assume Poynting-flux dominated jets on scales larger than a few pc and that the observed emission on these scales can be understood as energy dissipated in shocks…”
X-Ray Emission from Extragalactic Jets (2006, background): “Sikora et al. (2005) discuss this scenario, but deal only with the situation close to the black hole.”
Implications of very rapid TeV variability in blazars (2007, background): “…associated with cooling of the electrons (Sikora et al. 1994; Ghisellini et al. 1998), and c© 0000 RAS, MNRAS 000, 000–000 could mean that the acceleration mechanism is “particlestarved”, in the sense that the Poynting flux exceeds the kinetic energy flux in the flaring region (Sikora et al. 2005).”