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Formation of Planetary Nebula Lobes by Jets  [PDF]
Noam Soker
Physics , 2001,
Abstract: I conduct an analytical study of the interaction of jets, or a collimated fast wind (CFW), with a previously blown asymptotic giant branch (AGB) slow wind. Such jets (or CFWs) are supposedly formed when a compact companion, a main sequence star or a white dwarf, accretes mass from the AGB star, forms an accretion disk, and blows two jets. This type of flow, which is thought to shape bipolar planetary nebulae (PNe), requires 3-dimensional gas dynamical simulations, which are limited in the parameter space they can cover. By imposing several simplifying assumptions, I derive simple expressions which reproduce some basic properties of lobes in bipolar PNe, and which can be used to guide future numerical simulations. I quantitatively apply the results to two proto-PNe. I show that the jet interaction with the slow wind can form lobes which are narrow close to, and far away from, the central binary system, and which are wider somewhere in between. Jets that are recollimated and have constant cross section can form cylindrical lobes with constant diameter, as observed in several bipolar PNe. Close to their source, jets blown by main sequence companions are radiative; only further out they become adiabatic, i.e., they form high-temperature low-density bubbles that inflate the lobes. This implies that radiative cooling must be incorporated in numerical codes intended to study the formation of lobes in PNe.
Formation and destruction of jets in X-ray binaries  [PDF]
N. D. Kylafis,I. Contopoulos,D. Kazanas,D. M. Christodoulou
Physics , 2011, DOI: 10.1142/S2010194512004722
Abstract: Neutron-star and black-hole X-ray binaries (XRBs) exhibit radio jets, whose properties depend on the X-ray spectral state and history of the source. In particular, black-hole XRBs emit compact, steady radio jets when they are in the so-called hard state, the jets become eruptive as the sources move toward the soft state, disappear in the soft state, and re-appear when the sources return to the hard state. On the other hand, jets from neutron-star X-ray binaries are typically weaker radio emitters than the black-hole ones at the same X-ray luminosity and in some cases radio emission is detected in the soft state. Significant phenomenology has been accumulated so far regarding the spectral states of neutron-star and black-hole XRBs, and there is general agreement about the type of the accretion disk around the compact object in the various spectral states. Our aim is to investigate whether the phenomenology regarding the X-ray emission on one hand and the jet appearance and disappearance on the other can be put together in a consistent physical picture. It has been shown that the so-called Poynting-Robertson Cosmic Battery (PRCB) explains in a natural way the formation of magnetic fields in the disks of AGN and the ejection of jets. We investigate whether the PRCB can also explain the formation, destruction, and variability of jets in XRBs. We find excellent agreement between the conditions under which the PRCB is efficient (i.e., the type of the accretion disk) and the emission or destruction of the radio jet. The disk-jet connection in XRBs is explained in a natural way using the PRCB.
Formation of internal shock waves in bent jets  [PDF]
S. Mendoza,M. S. Longair
Physics , 2001, DOI: 10.1046/j.1365-8711.2002.05188.x
Abstract: We discuss the circumstances under which the bending of a jet can generate an internal shock wave. The analysis is carried out for relativistic and non-relativistic astrophysical jets. The calculations are done by the method of characteristics for the case of steady simple waves. This generalises the non-relativistic treatment first used by Icke (1991). We show that it is possible to obtain an upper limit to the bending angle of a jet in order not to create a shock wave at the end of the curvature. This limiting angle has a value of 75 degrees for non-relativistic jets with a polytropic index k = 4/3, 135 degrees for non-relativistic jets with k = 5/3) and 50 degrees for relativistic jets with k = 5/3. We also discuss under which circumstances jets will form internal shock waves for smaller deflection angles.
The role of AGN jets and intracluster magnetic fields in the formation and acceleration of cosmic rays  [PDF]
Nectaria A. B Gizani
Physics , 2012, DOI: 10.1017/S1743921311014815
Abstract: Using radio and X-ray data of two powerful radiogalaxies we attempt to find out the role that radio jets (in terms of composition and power) as well as intracluster magnetic fields play in the formation, propagation and acceleration of cosmic rays. For this study we have selected the powerful radio galaxies Hercules A and 3C\,310 because of the presence of ring-like features in their kpc-scale radio emission instead of the usual hotspots. These two FR1.5 lie at the center of galaxy cooling flow clusters in a dense environment. We observed the unique jets of Hercules both in kpc- (multifrequency VLA data) and pc-scales (EVN observations at 18 cm). We have also observed the core and inner jets of 3C310 at 18 cm using global VLBI. We report on the work in progress.
Pulsed Gas Jets for Formation of High-Intensity Cluster Beams  [PDF]
N. G. Korobeishchikov, A. E. Zarvin, V. V. Kalyada, A. A. Schmakov
Advances in Materials Physics and Chemistry (AMPC) , 2012, DOI: 10.4236/ampc.2012.24B009
Abstract: The possibility of using of pulsed supersonic gas jets for the formation of high intensity cluster ion beams are discusses. The results of experimental investigations of pulsed gases expansion are generalized in terms of dimensionless similarity parameters. The results of the experimental study of formation of an high-intensity cluster beam of argon are presented. The fundamental phenomenon influences on the main parameters of cluster beam (cluster size, intensity ect.) are considered.
Formation of Episodic Magnetically Driven Radiatively Cooled Plasma Jets in the Laboratory  [PDF]
F. Suzuki-Vidal,S. V. Lebedev,A. Ciardi,S. N. Bland,J. P. Chittenden,G. N. Hall,A. Harvey-Thompson,A. Marocchino,C. Ning,C. Stehle,A. Frank,E. G. Blackman,S. C. Bott,T. Ray
Physics , 2009, DOI: 10.1007/s10509-009-9981-1
Abstract: We report on experiments in which magnetically driven radiatively cooled plasma jets were produced by a 1 MA, 250 ns current pulse on the MAGPIE pulsed power facility. The jets were driven by the pressure of a toroidal magnetic field in a ''magnetic tower'' jet configuration. This scenario is characterized by the formation of a magnetically collimated plasma jet on the axis of a magnetic ''bubble'', confined by the ambient medium. The use of a radial metallic foil instead of the radial wire arrays employed in our previous work allows for the generation of episodic magnetic tower outflows which emerge periodically on timescales of ~30 ns. The subsequent magnetic bubbles propagate with velocities reaching ~300 km/s and interact with previous eruptions leading to the formation of shocks.
Ridge Formation Induced by Jets in $pp$ Collisions at 7 TeV  [PDF]
Rudolph C. Hwa,C. B. Yang
Physics , 2010, DOI: 10.1103/PhysRevC.83.024911
Abstract: An interpretation of the ridge phenomenon found in pp collisions at 7 TeV is given in terms of enhancement of soft partons due to energy loss of semihard jets. A description of ridge formation in nuclear collisions can directly be extended to pp collisions, since hydrodynamics is not used, and azimuthal anisotropy is generated by semihard scattering. Both the p_T and multiplicity dependencies are well reproduced. Some suggestions are made about other observables.
Formation of protostellar jets - effects of magnetic diffusion  [PDF]
Christian Fendt,Miljenko Cemeljic
Physics , 2002, DOI: 10.1051/0004-6361:20021442
Abstract: We investigate the evolution of a disk wind into a collimated jet under the influence of magnetic diffusivity, assuming that the turbulent pattern in the disk will also enter the disk corona and the jet. Using the ZEUS-3D code in the axisymmetry option we solve the time-dependent resistive MHD equations for a model setup of a central star surrounded by an accretion disk. We find that the diffusive jets propagate slower into the ambient medium. Close to the star we find that a quasi stationary state evolves after several hundred (weak diffusion) or thousand (strong diffusion) disk rotations. Magnetic diffusivity affects the protostellar jet structure as follows. The jet poloidal magnetic field becomes de-collimated. The jet velocity increases with increasing diffusivity, while the degree of collimation for the hydrodynamic flow remains more or less the same. We suggest that the mass flux is a proper tracer for the degree of jet collimation and find indications of a critical value for the magnetic diffusivity above which the jet collimation is only weak.
Formation and collimation of relativistic MHD jets - simulations and radio maps  [PDF]
Christian Fendt,Oliver Porth,Somayeh Sheikhnezami
Physics , 2013, DOI: 10.1142/S2010194514601902
Abstract: We present results of magnetohydrodynamic (MHD) simulations of jet formation and propagation, discussing a variety of astrophysical setups. In the first approach we consider simulations of relativistic MHD jet formation, considering jets launched from the surface of a Keplerian disk, demonstrating numerically - for the first time - the self-collimating ability of relativistic MHD jets. We obtain Lorentz factors up to about 10 while acquiring a high degree of collimation of about 1 degree. We then present synchrotron maps calculated from the intrinsic jet structure derived from the MHD jet formation simulation. We finally present (non-relativistic) MHD simulations of jet lauching, treating the transition between accretion and ejection. These setups include a physical magnetic diffusivity which is essential for loading the accretion material onto the outflow. We find relatively high mass fluxes in the outflow, of the order of 20-40 % of the accretion rate.
Bipolar jets launched from accretion disks. II. Formation of symmetric and asymmetric jets and counter jets  [PDF]
Christian Fendt,Somayeh Sheikhnezami
Physics , 2013, DOI: 10.1088/0004-637X/774/1/12
Abstract: We investigate the jet launching process from accretion disks extending our recent study (paper I) to a truly bipolar setup. We perform axisymmetric MHD simulations of the disk-jet interaction on a computational domain covering both hemispheres, in particular addressing the question of an intrinsically asymmetric origin of jet / counter jet systems. Treating both hemispheres simultaneously, we overcome the equatorial plane symmetry boundary condition used in most previous studies which naturally fosters a symmetric evolution. For the magnetic diffusivity prescription we apply an alpha-parametrisation, considering both, globally models of diffusivity, and local models. We first approve the quality of our numerical setup by generating perfectly symmetric jets, lasting over a 1000s of dynamical time scales. We then disturb the hemispheric symmetry in the disk, and investigate the subsequent evolution of the outflow. The evolution first leads to a substantial disk warping with electric currents intersecting the equatorial plane. We investigate two models, i) a disk with (initially) different thermal scale height in both hemispheres, and ii) a symmetric disk into which a local disturbance is injected in one hemisphere. In both cases the disk asymmetry results in asymmetric outflows with mass fluxes differing by 10-20%. We find up to 30% difference in mass flux between jet and counter jet for this setup, lasting over 1000s of dynamical time scales (i.e. lasting for the whole simulation). In summary, our results suggest that the jet asymmetries in protostellar and extragalactic jets can indeed be generated intrinsically and maintained over long time by disk asymmetries and the standard jet launching mechanism.
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