Radial wire array Z-pinches as a novel, compact x-ray source

Ampleford, D. J.; Jennings, Christopher; Bland, Simon; Лебедев, С. В.; Hall, G. N.; Suzuki-Vidal, F.

doi:10.1109/plasma.2008.4591000

Cited by 2 publications

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“…Lebedev 2005;Ampleford et al 2008) have also shown the development of conical shocks forming at the base and along the axis of the developed jet.…”

Section: Jets and Multiple Oblique Shocksmentioning

confidence: 99%

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Meli¹,

Biermann

2013

A&A

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Context. Shocks in jets and hot spots of active galactic nuclei (AGN) are one prominent class of possible sources of very high-energy cosmic-ray particles (above 10 18 eV). Extrapolating their spectrum to their plausible injection energy from some shock implies an enormous hidden energy for a spectrum of index ∼−2. Some analyses suggest the particles' injection spectrum at source to be as steep as −2.4 to −2.7, which exacerbates the problem, by a factor of 10 6 . Nevertheless, it seems implausible that more than at the very best 1/3 of the jet energy goes into the required flux of energetic particles, thus one would need to allow for the possibility that there is an energy problem, which we would like to address in this work. Aims. Sequences of consecutive oblique shock features, or conical shocks, have been theoretically predicted and eventually observed in many AGN jets. Based on that, we use by analogy the Comptonization effect and propose a scenario of a single injection of particles consecutively accelerated by several oblique shocks along the axis of an AGN jet. Methods. We developed a test-particle approximation Monte Carlo simulations to calculate particle spectra by acceleration at such a shock pattern while monitoring the efficiency of acceleration by calculating differential spectra. Results. We find that the first shock of a sequence of oblique shocks establishes a low-energy power-law spectrum with ∼E −2.7 . The following consecutive shocks push the spectrum up in energy, rendering flatter distributions with steep cut-offs, and characteristic depletion at low energies, which could explain the puzzling apparent extra source power. Conclusions. Our numerical calculations show a variation of spectral indices, a general spectral flattening, and starved spectra, which connect to the relativistic nature of the shocks, the multiple shock acceleration conditions, and the steepness of the magnetic field to the shock normal. This helps in understanding the jet-magnetic field geometry and the irregular or flat spectra observed in many AGN jets (e.g., CenA, 3C 279, PKS 1510-089). Furthermore, the E −2.4 − E −2.7 ultra-high-energy cosmic-ray injected source spectra claimed by many authors might be explained by the superposition of several, perhaps many, emission sources, all of which end their particle shock-acceleration sequence with flatter, starved spectra produced by two or more consecutive oblique shocks along their jets. It might also imply a mixed component of the accelerated particles above 10 19 eV. Moreover, the present acceleration model can explain the variability of inverted gamma-ray spectra observed in high redshifted flaring extragalactic sources.

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“…Lebedev 2005;Ampleford et al 2008) have also shown the development of conical shocks forming at the base and along the axis of the developed jet.…”

Section: Jets and Multiple Oblique Shocksmentioning

confidence: 99%

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Meli¹,

Biermann

2013

A&A

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“…Lebedev et al 2005;Ampleford et al 2008) have shown development of oblique or conical shocks forming at the base of a supersonic jet and along its axis. The latest observations have witnessed a development of standing or traveling shocks in many astrophysical objects, and most prominently in AGN jets (e.g.…”

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confidence: 99%

Relativistic jets and Ccsmic ray acceleration

Meli

2012

EAS Publications Series

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Abstract. Cosmic rays are accelerated in astrophysical plasmas which collide at supersonic speeds where shock waves are formed, and along with other instabilities, they compete for the dissipation and acceleration mechanisms. The diffusive acceleration mechanism plays a leading role in the explanation of very high energy cosmic rays observed. In this mechanism, particles are repeatedly gaining energy in multiple crossings of an astrophysical shock discontinuity, due to collisions with upstream and downstream magnetic scattering centers, resulting in a power-law spectrum extending up to very high energies. Relativistic jets and their shocks in Active Galactic Nuclei (AGN) is a prominent source for particle acceleration. Especially, relativistic single or multiple shocks have been theorized and observed along the jets of AGN and are claimed to be responsible for accelerating even the highest-energy cosmic rays observed. In this paper we will report and discuss the cosmic ray acceleration efficiency and properties of single or multiple shocks in the limit of relativistic plasmas in AGN jet environments.

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Radial wire array Z-pinches as a novel, compact x-ray source

Cited by 2 publications

References 0 publications

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Relativistic jets and Ccsmic ray acceleration

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