Episodic Magnetic Bubbles and Jets: Astrophysical Implications From Laboratory Experiments

Ciardi, A.; Lebedev, S. V.; Frank, Adam; Suzuki-Vidal, F.; Hall, G. N.; Bland, S. N.; Harvey‐Thompson, A. J.; Blackman, Eric G.; Camenzind, M.

doi:10.1088/0004-637x/691/2/l147

Cited by 78 publications

(69 citation statements)

References 32 publications

(30 reference statements)

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“…Recently the use of a radial metallic foil on a Z-pinch driver has shown the formation of episodic plasma jets [25][26][27], each episode presenting similar dynamics to the single-episode jets seen in radial wire array experiments [22]. These episodic outflows can address open astrophysical questions regarding the spatial and temporal variability observed in protostellar jets.…”

Section: Introductionmentioning

confidence: 92%

Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

et al. 2010

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We present experimental results of the formation of magnetically driven plasma jets, showing for the first time a way of producing episodic jet/ouflows in the laboratory. The jets are produced using a 6.5 µm thick aluminum disc (a radial foil), which is subjected to the 1 MA, 250 ns current pulse from the MAGPIE generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533(1996]. The early time motion of the foil is characterized by the bulk motion of the mass due to the magnetic pressure, together with the formation of a surface plasma following the direction of the J × B force. A low density plasma fills the region above the foil preceding the formation of subsequent magnetically driven jets on the axis of expanding magnetic bubbles. The outflows emerge in timescales of ∼30-40 ns and their episodic nature is the result of current reconnection in the foil, aided by the formation of current-driven instabilities in the jet and the distribution of mass available from the foil. The additional inductance due to the new current path inside the cavities was measured using an inductive probe, allowing to estimate the energy balance associated with the episodes. The measured temperature of the compressed jet resulted in Te∼300 eV and a magnetic Reynolds number of ReM ∼200-1000, allowing the experiments to be in the regime relevant for scaled representations of astrophysical outflows.

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Section: Introductionmentioning

confidence: 92%

Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

et al. 2010

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“…Based on recent laboratory experiments of radiatively cooled plasma jets, Ciardi et al (2009) propose yet another possible ejection mechanism for the DG Tau jet. Starting from a highly wound-up field configuration with |B φ | ∝ r −1 B p and a strong axial current, two outflow components are generated: a magnetic bubble (or cavity) accelerated by gradients of the magnetic pressure and surrounded by a shell of swept-up ambient material, and a magnetically confined narrow jet on the bubble axis.…”

Section: Episodic Magnetic Bubblesmentioning

confidence: 99%

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Agra-Amboage

Dougados

Cabrit

et al. 2011

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Context. The origin of protostellar jets as well as their impact on the regulation of angular momentum and the inner disk physics are still crucial open questions in star formation. Aims. We aim to test the different proposed ejection processes in T Tauri stars through high-angular resolution observations of forbidden-line emission from the inner DG Tauri microjet. Methods. We present spectro-imaging observations of the DG Tauri jet obtained with SINFONI/VLT in the lines of [Fe ii]λ1.64 μm, 1.53 μm with 0. 15 angular resolution and R = 3000 spectral resolution. We analyze the morphology and kinematics, derive electronic densities and mass-flux rates and discuss the implications for proposed jet launching models. Results. (1) We observe an onion-like velocity structure in [Fe ii] in the blueshifted jet, similar to that observed in optical lines. Highvelocity (HV) gas at -200 km s −1 is collimated inside a half-opening angle of 4 • and medium-velocity (MV) gas at -100 km s −1 in a cone with an half-opening angle 14.• (2) Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. (3) The redshifted jet is detected only beyond 0. 7 from the star, yielding revised constraints on the disk surface density. (4) From comparison to [O i] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km s −1 . (5) The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are 1.6 ± 0.8 × 10 −8 M yr −1 , representing 0.02−0.2 of the disk accretion rate. Conclusions. The medium-velocity conical [Fe ii] flow in the DG Tau jet is too fast and too narrow to trace photo-evaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the "conical magnetospheric wind". The level of Fe gas phase depletion in the DG Tau medium-velocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25−1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the [Fe ii] medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity [Fe ii] flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component.

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“…These experiments reproduce some features of the actual YSO jets such as jet velocities, temperatures, and cooling effects. Comparisons between laboratory jets produced by pulsed-power Z-pinch machines with simulations have been discussed by Ciardi et al (2009). The disadvantage of these techniques is their inability to produce long collimated jets, where long means orders of magnitude longer than the width of the formation region.…”

Section: Introductionmentioning

confidence: 99%

The hydrodynamics of astrophysical jets: scaled experiments and numerical simulations

Belan

Massaglia

Tordella

et al. 2013

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Context. In this paper we study the propagation of hypersonic hydrodynamic jets (Mach number >5) in a laboratory vessel and make comparisons with numerical simulations of axially symmetric flows with the same initial and boundary conditions. The astrophysical context is that of the jets originating around young stellar objects (YSOs). Aims. In order to gain a deeper insight into the phenomenology of YSO jets, we performed a set of experiments and numerical simulations of hypersonic jets in the range of Mach numbers from 10 to 20 and for jet-to-ambient density ratios from 0.85 to 5.4, using different gas species and observing jet lengths of the order of 150 initial radii or more. Exploiting the scalability of the hydrodynamic equations, we intend to reproduce the YSO jet behaviour with respect to jet velocity and elapsed times. In addition, we can make comparisons between the simulated, the experimental, and the observed morphologies. Methods. In the experiments the gas pressure and temperature are increased by a fast, quasi-isentropic compression by means of a piston system operating on a time scale of tens of milliseconds, while the gas density is visualized and measured by means of an electron beam system. We used the PLUTO software for the numerical solution of mixed hyperbolic/parabolic conservation laws targeting high Mach number flows in astrophysical fluid dynamics. We considered axisymmetric initial conditions and carried out numerical simulations in cylindrical geometry. The code has a modular flexible structure whereby different numerical algorithms can be separately combined to solve systems of conservation laws using the finite volume or finite difference approach based on Godunovtype schemes. Results. The agreement between experiments and numerical simulations is fairly good in most of the comparisons. The resulting scaled flow velocities and elapsed times are close to the ones shown by observations. The morphologies of the density distributions agree with the observed ones as well. Conclusions. The laboratory and the simulated hypersonic jets are all pressure matched, i.e. their axial regions are almost isentropic at the nozzle exit. They maintain their collimation for long distances in terms of the initial jet radii, without including magnetic confinement effects. This yields a qualitatively good agreement with the observed YSO jet morphologies. It remains to be seen what happens when non-axially symmetric perturbations of the flow are imposed at the nozzle, both in the experiment and in the simulation.

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Episodic Magnetic Bubbles and Jets: Astrophysical Implications From Laboratory Experiments

Cited by 78 publications

References 32 publications

Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

The hydrodynamics of astrophysical jets: scaled experiments and numerical simulations

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