Time-resolved velocity and ion sound speed measurements from simultaneous bow shock imaging and inductive probe measurements

Datta, R.; Russell, D. R.; Clayson, Thomas; Chittenden, J. P.; Lebedev, S. V.; Hare, Jack

doi:10.1063/5.0098823

Cited by 7 publications

(12 citation statements)

References 25 publications

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“…Furthermore, we infer the flow velocity from the time delay in the probe signals (Datta et al. 2022), giving us an estimated upstream Alfvén Mach number of . Similarly, for a eV aluminium plasma (Suttle et al.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…2019; Datta et al. 2022). We position the inductive probe to measure the azimuthal magnetic field – the normals to the surfaces of the loops lie along the magnetic field.…”

Section: Experimental and Diagnostic Set-upmentioning

confidence: 99%

“…The ion-ion MFP of the ablating plasma is also small (λ ii ∼ 10 −3 mm), so the plasma is highly collisional (Suttle et al 2019). The flow velocity in similar set-ups is typically supersonic (M S ∼ 3 − 5), super-Alfvénic (M A ∼ 2) and superfast magnetosonic (M FMS ∼ 2) (Burdiak et al 2017;Russell et al 2022). The collision of these supersonic outflows with the obstacle generates a detached bow shock.…”

Section: Experimental and Diagnostic Set-upmentioning

confidence: 99%

“…Previous experimental work on collisional shocks has shown that magnetic fields can modify the structure of collisional plasma shocks in two primary ways -either via the generation of magnetohydrodynamic (MHD) shocks, (Lebedev et al 2014;Russell et al 2022) or via magnetic flux pile-up (Burdiak et al 2017;Suttle et al 2019). In MHD shocks, the magnetic field can change discontinuously across the shock front, resulting in complicated anisotropic shock structures, whose morphology depends not only on the velocity of the upstream flow relative to the three MHD wave speeds (fast, slow and Alfvén waves), but also on the orientation of the upstream magnetic field relative to the shock front (De Sterck et al 1998;De Sterck & Poedts 2000;Verigin et al 2001;Goedbloed, Keppens & Poedts 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In MHD shocks, the magnetic field can change discontinuously across the shock front, resulting in complicated anisotropic shock structures, whose morphology depends not only on the velocity of the upstream flow relative to the three MHD wave speeds (fast, slow and Alfvén waves), but also on the orientation of the upstream magnetic field relative to the shock front (De Sterck et al 1998;De Sterck & Poedts 2000;Verigin et al 2001;Goedbloed, Keppens & Poedts 2010). Recent experiments have also investigated the role of resistive dissipation in MHD shock transitions through the formation of subcritical collisional shocks (Russell et al 2022).…”

Section: Introductionmentioning

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%

“…2019; Datta et al. 2022). We position the inductive probe to measure the azimuthal magnetic field – the normals to the surfaces of the loops lie along the magnetic field.…”

Section: Experimental and Diagnostic Set-upmentioning

confidence: 99%

Section: Experimental and Diagnostic Set-upmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

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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Observation of subcritical shocks in a collisional laboratory plasma: scale dependence near the resistive length

Russell,

Burdiak,

Carroll-Nellenback

et al. 2023

J. Plasma Phys.

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We present a study of subcritical shocks in a highly collisional laboratory plasma with a dynamically significant magnetic field. Shocks were produced by placing cylindrical obstacles into the supermagnetosonic ( $M_{{\rm MS}} \sim 1.9$ ) outflow from an inverse wire array z-pinch at the MAGPIE pulsed power facility ( $n_{e} \sim 8.5 \times 10^{17}\,{\rm cm}^{-3}$ , $v \sim 45\,{\rm km}\,{\rm s}^{-1}$ ). We demonstrate the existence of subcritical shocks in this regime and find that secondary stagnation shocks form in the downstream which we infer from interferometry and optical Thomson scattering measurements are hydrodynamic in nature. The subcritical shock width is found to be approximately equal to the resistive diffusion length and we demonstrate the absence of a jump in hydrodynamic parameters. Temperature measurements by collective optical Thomson scattering showed little temperature change across the subcritical shock ( ${<}10\,\%$ of the ion kinetic energy) which is consistent with a balance between adiabatic and Ohmic heating and radiative cooling. We demonstrate the absence of subcritical shocks when the obstacle diameter is less than the resistive diffusion length due to decoupling of the magnetic field from the plasma. These findings are supported by magnetohydrodynamic simulations using the Gorgon and AstroBEAR codes and discrepancies between the simulations and experiment are discussed.

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Simulations of radiatively cooled magnetic reconnection driven by pulsed power

Datta,

Crilly,

Chittenden

et al. 2024

J. Plasma Phys.

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Magnetic reconnection is an important process in astrophysical environments, as it reconfigures magnetic field topology and converts magnetic energy into thermal and kinetic energy. In extreme astrophysical systems, such as black hole coronae and pulsar magnetospheres, radiative cooling modifies the energy partition by radiating away internal energy, which can lead to the radiative collapse of the reconnection layer. In this paper, we perform two- and three-dimensional simulations to model the MARZ (Magnetic Reconnection on Z) experiments, which are designed to access cooling rates in the laboratory necessary to investigate reconnection in a previously unexplored radiatively cooled regime. These simulations are performed in GORGON, an Eulerian two-temperature resistive magnetohydrodynamic code, which models the experimental geometry comprising two exploding wire arrays driven by 20 MA of current on the Z machine (Sandia National Laboratories). Radiative losses are implemented using non-local thermodynamic equilibrium tables computed using the atomic code Spk, and we probe the effects of radiation transport by implementing both a local radiation loss model and $P_{1/3}$ multi-group radiation transport. The load produces highly collisional, super-Alfvénic (Alfvén Mach number $M_A \approx 1.5$ ), supersonic (Sonic Mach number $M_S \approx 4-5$ ) strongly driven plasma flows which generate an elongated reconnection layer (Aspect Ratio $L/\delta \approx 100$ , Lundquist number $S_L \approx 400$ ). The reconnection layer undergoes radiative collapse when the radiative losses exceed the rates of ohmic and compressional heating (cooling rate/hydrodynamic transit rate = $\tau _{\text {cool}}^{-1}/\tau _{H}^{-1}\approx 100$ ); this generates a cold strongly compressed current sheet, leading to an accelerated reconnection rate, consistent with theoretical predictions. Finally, the current sheet is also unstable to the plasmoid instability, but the magnetic islands are extinguished by strong radiative cooling before ejection from the layer.

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Time-resolved velocity and ion sound speed measurements from simultaneous bow shock imaging and inductive probe measurements

Cited by 7 publications

References 25 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

Observation of subcritical shocks in a collisional laboratory plasma: scale dependence near the resistive length

Simulations of radiatively cooled magnetic reconnection driven by pulsed power

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