Numerical simulations of Mach stem formation via intersecting bow shocks

Hansen, Edward C.; Frank, Adam; Hartigan, Patrick; Yirak, Kristopher

doi:10.1016/j.hedp.2014.12.005

Cited by 4 publications

(7 citation statements)

References 19 publications

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“…An important application of the new non-equilibrium cooling routines in AstroBEAR is simulations of HH objects. In previous studies, we have run simulations of pulsed jets (Hansen et al 2015b) and interacting bow shocks (Hansen et al 2017). The example outflow and synthetic emission map we show here is similar to the simulations from the latter work.…”

Section: Applications To Hh Objectssupporting

confidence: 73%

“…We are currently using the new non-equilibrium cooling functionality in other research projects such as 3-D pulsed jets which will expand on the work done in Hansen et al (2015b). There is much research that can be done with the current implementation, but further improvements to cooling -25in AstroBEAR can still be made.…”

Section: Discussionmentioning

confidence: 99%

“…For any simulation that uses cooling, it is important to know the cooling lengths of the strongest radiative shocks within the grid because stronger shocks cool faster and will have a shorter L cool . As discussed in Hansen et al (2015b), the cooling length resolution is crucial to resolving instabilities caused directly or indirectly by strong cooling. Yirak et al (2010) found that a cooling length resolution of at least 10 cells per L cool was required to resolve such instabilities.…”

Section: Testing Astrobear's Cooling Routinesmentioning

confidence: 99%

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Erratum: Simulating radiative magnetohydrodynamical flows with astrobear: implementation and applications of non-equilibrium cooling

Hansen

Hartigan

Frank

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Radiative cooling plays a crucial role in the dynamics of many astrophysical flows, and is particularly important in the dense shocked gas within Herbig-Haro (HH) objects and stellar jets. Simulating cooling processes accurately is necessary to compare numerical simulations with existing and planned observations of HH objects, such as those from the Hubble Space Telescope and the James Webb Space Telescope. In this paper we discuss a new, non-equilibrium cooling scheme we have implemented into the 3-D magnetohydrodynamic (MHD) code AstroBEAR. The new cooling function includes ionization, recombination, and excitation of all the important atomic species that cool below 10000 K. We tested the routine by comparing its predictions with those from the well-tested 1-D Cox-Raymond shock code (Raymond 1979). The results show that AstroBEAR accurately tracks the ionization fraction, temperature, and other MHD variables for all low-velocity ( 90 km/s) magnetized radiative shock waves. The new routine allows us to predict synthetic emission maps in all the bright forbidden and permitted lines observed in stellar jets, including Hα, [N II], [O I], and [S II]. We present an example as to how these synthetic maps facilitate a direct comparison with narrowband images of HH objects.

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Section: Applications To Hh Objectssupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Testing Astrobear's Cooling Routinesmentioning

confidence: 99%

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Erratum: Simulating radiative magnetohydrodynamical flows with astrobear: implementation and applications of non-equilibrium cooling

Hansen

Hartigan

Frank

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Since Mach stems are planar shocks, gas that crosses it will be heated to higher temperatures compared to the oblique bow shock. As a result, enhanced emission will be produced relative to that from a single bow shock (Hansen et al 2015a). Such intersections can also exhibit motion that is lateral to the overall flow which appears to be seen in the observations of HH objects such as HH 34.…”

Section: Introductionmentioning

confidence: 94%

“…Thus, we begin by considering features of the simpler problem of two interacting stationary bows. This problem was studied via 2-D numerical simulations by Hansen et al (2015a) whose goal was to determine the minimum critical angle for Mach stem formation. We review this problem in the first subsection below, and in the second subsection, we describe the relevant hydrodynamic instabilities and how they should affect the observed flow and emission.…”

Section: Theorymentioning

confidence: 99%

The Shock Dynamics of Heterogeneous YSO Jets:3D Simulations Meet Multi-epoch Observations

Hansen

Frank

Hartigan

et al. 2017

ApJ

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High-resolution observations of young stellar object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper, we report results of 3D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale dynamics by imposing velocity differences between spherical, over-dense regions, which then lead to the formation of bow shocks as faster clumps overtake slower material. We show that much of the spatial structure apparent in emission line images of jets arises from the dynamics and interactions of these bow shocks. Our simulations show a variety of time-dependent features, including bright knots associated with Mach stems where the shocks intersect, a "frothy" emission structure that arises from the presence of the Nonlinear Thin Shell Instability along the surfaces of the bow shocks, and the merging and fragmentation of clumps. Our simulations use a new non-equilibrium cooling method to produce synthetic emission maps in Hα and [S II]. These are directly compared to multi-epoch Hubble Space Telescope observations of Herbig-Haro jets. We find excellent agreement between features seen in the simulations and the observations in terms of both proper motion and morphologies. Thus we conclude that YSO jets may be dominated by heterogeneous structures and that interactions between these structures and the shocks they produce can account for many details of YSO jet evolution.

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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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Numerical simulations of Mach stem formation via intersecting bow shocks

Cited by 4 publications

References 19 publications

Erratum: Simulating radiative magnetohydrodynamical flows with astrobear: implementation and applications of non-equilibrium cooling

Erratum: Simulating radiative magnetohydrodynamical flows with astrobear: implementation and applications of non-equilibrium cooling

The Shock Dynamics of Heterogeneous YSO Jets:3D Simulations Meet Multi-epoch Observations

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

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