Computational extended magneto-hydrodynamical study of shock structure generated by flows past an obstacle

Zhao, Xuan; Seyler, C. E.

doi:10.1063/1.4923426

Cited by 8 publications

(3 citation statements)

References 34 publications

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“…2013). Extended-MHD simulations have previously demonstrated widening of MHD bow shocks around obstacles with size comparable to the ion inertial length, and this modification of the shock shape is associated with a suppression of the current in the postshock low density region by the Hall term (Zhao & Seyler 2015). However, it remains unclear if Hall effects can account for the observed shock anisotropy in the experimental bow shock, and future work will aim to investigate this with extended-MHD simulations.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…When ions and electrons decouple at the ion skin depth, the magnetic field is no longer frozen into the ion fluid, and two-fluid effects, in particular the Hall term in Ohm's law, may become important (Eastwood et al 2007;Shaikhislamov et al 2013). Extended-MHD simulations have previously demonstrated widening of MHD bow shocks around obstacles with size comparable to the ion inertial length, and this modification of the shock shape is associated with a suppression of the current in the postshock low density region by the Hall term j × B/en (Zhao & Seyler 2015). However, it remains unclear if Hall effects can account for the observed shock anisotropy in the experimental bow shock, and future work will aim to investigate this with extended-MHD simulations.…”

Section: Effect Of Magnetic Draping and Shock Anisotropymentioning

confidence: 99%

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The structure of 3-D collisional magnetized bow shocks in pulsed-power-driven plasma flows

et al. 2022

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We investigate three-dimensional (3-D) bow shocks in a highly collisional magnetized aluminium plasma, generated during the ablation phase of an exploding wire array on the MAGPIE facility (1.4 MA, 240 ns). Ablation of plasma from the wire array generates radially diverging, supersonic ( $M_S \sim 7$ ), super-Alfvénic ( $M_A > 1$ ) magnetized flows with frozen-in magnetic flux ( $R_M \gg 1$ ). These flows collide with an inductive probe placed in the flow, which serves both as the obstacle that generates the magnetized bow shock, and as a diagnostic of the advected magnetic field. Laser interferometry along two orthogonal lines of sight is used to measure the line-integrated electron density. A detached bow shock forms ahead of the probe, with a larger opening angle in the plane parallel to the magnetic field than in the plane normal to it. Since the resistive diffusion length of the plasma is comparable to the probe size, the magnetic field decouples from the ion fluid at the shock front and generates a hydrodynamic shock, whose structure is determined by the sonic Mach number, rather than the magnetosonic Mach number of the flow. The 3-D simulations performed using the resistive magnetohydrodynamic (MHD) code Gorgon confirm this picture, but under-predict the anisotropy observed in the shape of the experimental bow shock, suggesting that non-MHD mechanisms may be important for modifying the shock structure.

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Section: Discussion Of Resultsmentioning

confidence: 99%

Section: Effect Of Magnetic Draping and Shock Anisotropymentioning

confidence: 99%

The structure of 3-D collisional magnetized bow shocks in pulsed-power-driven plasma flows

et al. 2022

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“…Perseus has been used previously to study the interaction of magnetised flows with obstacles. 16 Simulation results within 16 showed that the Hall term was important for the magnetotail structure behind the obstacles, but that it had no impact on the bow shock stand-off distance. Simulations of the present experiments using Perseus show qualitative agreement with the global structure of well-developed bow shocks.…”

Section: -7mentioning

confidence: 99%

The structure of bow shocks formed by the interaction of pulsed-power driven magnetised plasma flows with conducting obstacles

et al. 2017

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We present an experimental study of the development and structure of bow shocks produced by the interaction of a magnetised, collisional, super-Alfv enic plasma flow with conducting cylindrical obstacles. The plasma flow with an embedded, frozen-in magnetic field (Re M $ 20) is produced by the current-driven ablation of fine aluminium wires in an inverse, exploding wire array z-pinch. We show that the orientation of the embedded field with respect to the obstacles has a dramatic effect on the bow shock structure. When the field is aligned with the obstacle, a sharp bow shock is formed with a global structure that is determined simply by the fast magneto-sonic Mach number. When the field is orthogonal to the obstacle, magnetic draping occurs. This leads to the growth of a magnetic precursor and the subsequent development of a magnetised bow shock that is mediated by two-fluid effects, with an opening angle and a stand-off distance, that are both many times larger than in the parallel geometry. By changing the field orientation, we change the fluid regime and physical mechanisms that are responsible for the development of the bow shocks. MHD simulations show good agreement with the structure of well-developed bow shocks. However, collisionless, two-fluid effects will need to be included within models to accurately reproduce the development of the shock with an orthogonal B-field. Published by AIP Publishing.

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Revisiting the thermal effect on shock wave propagation in weakly ionized plasmas

Zhou

Yang

2016

Physics of Plasmas

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Many researchers have investigated shock propagation in weakly ionized plasmas and observed the following anomalous effects: shock acceleration, shock recovery, shock weakening, shock spreading, and splitting. It was generally accepted that the thermal effect can explain most of the experimental results. However, little attention was paid to the shock recovery. In this paper, the shock wave propagation in weakly ionized plasmas is studied by fluid simulation. It is found that the shock acceleration, weakening, and splitting appear after it enters the plasma (thermal) region. The shock splits into two parts right after it leaves the thermal region. The distance between the splitted shocks keeps decreasing until they recover to one. This paper can explain a whole set of features of the shock wave propagation in weakly ionized plasmas. It is also found that both the shock curvature and the splitting present the same photoacoustic deflection (PAD) signals, so they cannot be distinguished by the PAD experiments.

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Computational extended magneto-hydrodynamical study of shock structure generated by flows past an obstacle

Cited by 8 publications

References 34 publications

The structure of 3-D collisional magnetized bow shocks in pulsed-power-driven plasma flows

The structure of 3-D collisional magnetized bow shocks in pulsed-power-driven plasma flows

The structure of bow shocks formed by the interaction of pulsed-power driven magnetised plasma flows with conducting obstacles

Revisiting the thermal effect on shock wave propagation in weakly ionized plasmas

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