Showing papers by "Arnaud Ferrari published in 1993"
TL;DR: In this paper, the feasibility of extracting protons from the halo of a high energy beam by means of a bent silicon crystal has been investigated, and the present results are promising in view of beam extraction from future multi-TeV proton accelerators.
83 citations
TL;DR: In this paper, the effects of radiation losses on the instability pattern of two radiating fluids in relative motion were investigated in plane geometry and in the vortex-sheet approximation, and it was found that the principal effect is the suppression of the cutoff at Mach number M = 2√2, typical of the adiabatic Kelvin-Helmholtz mode.
Abstract: The linear Kelvin–Helmholtz stability regime of two radiating fluids in relative motion is discussed. The study is carried out in plane geometry and in the vortex‐sheet approximation. Attention is focused on the effects of radiation losses on the instability pattern: it is found that the principal effect is the suppression of the cutoff at Mach number M=2√2, typical of the adiabatic Kelvin–Helmholtz mode; in particular radiation effects are small on the instability below the cutoff, while they become dominant above. Radiating fluids are also typically affected by thermal instability. In fact thermal modes are found also in the present case: they may have growth rates comparable to the Kelvin–Helmholtz instability above the cutoff.
12 citations
TL;DR: In this article, a linear study of the radiative instability driven by synchrotron emission in astrophysical plasmas is presented, where the authors consider the case of a non-Maxwellian distribution function and follow its time evolution consistently.
Abstract: We present a linear study of the radiative instability driven by synchrotron emission in astrophysical plasmas. The novelty in this work is to consider the case of a non-Maxwellian distribution function and follow its time evolution consistently. We find unstable filamentation modes for any value of the spectral index, with increasing growth rate going from steep to flat spectra, provided that the plasma β is larger than unity. We discuss our results in the context of the formation of the filamentary structures observed in jets and lobes of extended radio sources
6 citations
01 Jan 1993
TL;DR: In this article, the authors studied the nonlinear behavior of such instabilities solving in a consistent way the equation of evolution of the distribution function of the emitting particles, following the hypothesis that such structures could be formed by thermal instabilities driven by synchrotron radiation in a relativistic plasma.
Abstract: Recent high resolution optical and radio observations of extragalactic sources show strong filamentary inhomogeneities of the emitting plasma, in their jets and lobes Following the hypothesis that such structures could be formed by thermal instabilities driven by synchrotron radiation in a relativistic plasma (Simon and Axford, 1967), we study the nonlinear behaviour of such instabilities solving in a consistent way the equation of evolution of the distribution function of the emitting particles
01 Jan 1993
TL;DR: In this article, the nonlinear evolution of Kelvin-Helmholtz instabilities in a cylindrical jet by numerical methods is studied and the separation between the shock waves is of the order of that observed in the case of knots in stellar jets.
Abstract: We study the nonlinear evolution of Kelvin-Helmholtz instabilities in a cylindrical jet by numerical methods. In light jets, the instability saturates, leading to the formation of periodic shock structures, while, in heavy jets, it leads to a disruption of the jet. The separation between the shock waves is of the order of that observed in the case of knots in stellar jets. We discuss our results in the context of models for the interpretation of such knots.