The Stability of Current-Carrying Jets

Appl, S.; Camenzind, M.

doi:10.1007/978-3-642-77566-6_109

Cited by 25 publications

(35 citation statements)

References 6 publications

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“…We used two independent ideal MHD stability codes, described in detail elsewhere (Appl & Camenzind 1992;Appl 1996;Appl et al 2000;Nijboer et al 1997). In both codes, an eigenvalue problem for an infinitely long cylindrical jet is solved using a normal mode expansion for the perturbed quantities of the form f ðrÞ exp½iðm þ kz À !tÞ .…”

Section: Stability Studymentioning

confidence: 99%

“…In both codes, an eigenvalue problem for an infinitely long cylindrical jet is solved using a normal mode expansion for the perturbed quantities of the form f ðrÞ exp½iðm þ kz À !tÞ . In Appl & Camenzind (1992), a temporal approach is taken in the ZYLSPEK code, where a complex frequency ! ¼ !…”

Section: Stability Studymentioning

confidence: 99%

“…In such jets, the magnetic tension due to the azimuthal field component can provide an effective collimation mechanism (see discussion in x 2 of Appl & Camenzind 1992). Such helical magnetic configurations have a nonzero electric current density.…”

mentioning

confidence: 99%

“…Such helical magnetic configurations have a nonzero electric current density. An ideal stability study has shown that current-carrying jets have KH modes that are slightly stabilized when compared to configurations having a uniform longitudinal magnetic field with the same fast magnetosonic Mach number (Appl & Camenzind 1992). On the other hand, such jets are also liable to other, pure MHD instabilities driven by the current density parallel to the magnetic field and by the thermal pressure gradient.…”

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confidence: 99%

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Interplay between Kelvin‐Helmholtz and Current‐driven Instabilities in Jets

Baty

Keppens

2002

ApJ

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We investigate, by means of three-dimensional compressible magnetohydrodynamic numerical simulations, the interaction of Kelvin-Helmholtz (KH) and current-driven (CD) instabilities in a magnetized cylindrical jet configuration. The jet has a supersonic axial flow, sheared in the radial direction, and is embedded in a helical magnetic field. The strength of the axial magnetic field component is chosen to be weak, in accord with the '' weak field regime '' previously defined by Ryu, Jones, & Frank for uniformly magnetized configurations. We follow the time evolution of a periodic section where the jet surface is perturbed at m ¼ AE1 azimuthal mode numbers. A m ¼ À1 KH surface mode linearly develops dominating the m ¼ þ1 KH one, in agreement with results obtained using an independent ideal stability code. This lifted degeneracy, because of the presence of the helical field, leads nonlinearly to clear morphological differences in the jet deformation as compared to uniformly magnetized configurations. As predicted by stability results, a m ¼ À1 CD instability also develops linearly inside the jet core for configurations having a small enough magnetic pitch length. As time proceeds, this magnetic mode interacts with the KH vortical structures and significantly affects the further nonlinear evolution. The magnetic field deformation induced by the CD instability provides a stabilizing effect through its azimuthal component B . This helps to saturate the KH vortices in the vicinity of the jet surface. Beyond saturation, the subsequent disruptive effect on the flow is weaker than in cases having similar uniform and helical magnetic field configurations without the CD mode. We discuss the implications of this stabilizing mechanism for the stability of astrophysical jets.

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Section: Stability Studymentioning

confidence: 99%

Section: Stability Studymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Interplay between Kelvin‐Helmholtz and Current‐driven Instabilities in Jets

Baty

Keppens

2002

ApJ

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“…Extensive analyses have been performed for fluid jets, e.g., Ferrari et al (1978); Hardee (1979); Birkinshaw (1984); Hardee (1987); Hardee (2000), considered the effects of a velocity shear layer (Birkinshaw 1991b), and rotation (Bodo et al 1996). Additional investigations added magnetic fields parallel to the flow velocity, e.g., Ferrari et al (1980);Ferrari et al (1981) ;Ferrari & Trussoni (1983); Ray (1981); Londrillo (1985); Trussoni et al (1988); Hardee (2007), and considered the addition of toroidal magnetic fields, e.g., Cohn (1983);Feidler & Jones (1984); Appl & Camenzind (1992). Relativistic jet simulations have found growth rates, e.g., Perucho et al (2004a); Perucho et al (2004b); Mizuno et al (2007), and jet structure, e.g., Hardee et al (1998); Hardee et al (2001); Agudo et al (2001); Hardee & Hughes (2003), predicted theoretically.…”

Section: Kelvin-helmholtz Instabilitymentioning

confidence: 99%

The stability of astrophysical jets

Hardee

2010

Proc. IAU

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Abstract. Jets are produced by young stellar objects (YSOs), by black hole binary star system "microquasars" (µQSOs), by active galactic nuclei (AGN), are associated with neutron stars and pulsar wind nebulae (PWNe), and are thought responsible for the gamma-ray bursts (GRBs). An understanding of these outflows must include how they are launched and collimated into jets, and how they propagate to large distances. Jets be they Poynting flux and/or kinetic flux dominated are current driven (CD) and/or Kelvin-Helmholtz (KH) velocity shear driven unstable. Here I present some of the work that is leading to a better understanding of the properties required for the observed relative stability of astrophysical jets.

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Signatures of helical jets

Steffen

1997

Vistas in Astronomy

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Observational signatures of helical jets can be found in some X-ray binaries (XRB), planetary nebulae, Herbig-Haro objects and in jets of active galactic nuclei (AGN). For the prototypical XRB SS433 a kinematic model of precessing jets has been applied very successfully and yielded a determination of its distance which is independent of conventional methods. In galactic jets precession appears to be the predominant mechanism for the production of observed helical signatures. In extragalactic jets other mechanisms seem to be similarly frequent. As a result of their strong dependence on the direction of motion with respect to the observer, special relativistic effects can be pronounced in helical jets. These have to be taken into account in AGN-jets and the newly discovered galactic sources which show apparent superluminal motion. Since the galactic superluminal jets are located in a binary system, jet precession is very likely in these sources. In this paper I review the main structural and kinematic signatures of helical jets and briefly mention the physical mechanisms behind them. I will present kinematic simulations of relativistic jets which are helically bent or have an internal helical flow field.

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The Stability of Current-Carrying Jets

Cited by 25 publications

References 6 publications

Interplay between Kelvin‐Helmholtz and Current‐driven Instabilities in Jets

Interplay between Kelvin‐Helmholtz and Current‐driven Instabilities in Jets

The stability of astrophysical jets

Signatures of helical jets

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