Astrophysical Simulations Research Articles

RASCAS: RAdiation SCattering in Astrophysical Simulations

Context. Resonant lines are powerful probes of the interstellar and circumgalactic medium of galaxies. Their transfer in gas being a complex process, the interpretation of their observational signatures, either in absorption or in emission, is often not straightforward. Numerical radiative transfer simulations are needed to accurately describe the travel of resonant line photons in real and in frequency space, and to produce realistic mock observations. Aims. This paper introduces RASCAS, a new public 3D radiative transfer code developed to perform the propagation of any resonant line in numerical simulations of astrophysical objects. RASCAS was designed to be easily customisable and to process simulations of arbitrarily large sizes on large supercomputers. Methods. RASCAS performs radiative transfer on an adaptive mesh with an octree structure using the Monte Carlo technique. RASCAS features full MPI parallelisation, domain decomposition, adaptive load-balancing, and a standard peeling algorithm to construct mock observations. The radiative transport of resonant line photons through different mixes of species (e.g. H I, Si II, Mg II, Fe II), including their interaction with dust, is implemented in a modular fashion to allow new transitions to be easily added to the code. Results. RASCAS is very accurate and efficient. It shows perfect scaling up to a minimum of a thousand cores. It has been fully tested against radiative transfer problems with analytic solutions and against various test cases proposed in the literature. Although it was designed to describe accurately the many scatterings of line photons, RASCAS may also be used to propagate photons at any wavelength (e.g. stellar continuum or fluorescent lines), or to cast millions of rays to integrate the optical depths of ionising photons, making it highly versatile.

Simulating Turbulence-aided Neutrino-driven Core-collapse Supernova Explosions in One Dimension

Abstract The core-collapse supernova (CCSN) mechanism is fundamentally 3D, with instabilities, convection, and turbulence playing crucial roles in aiding neutrino-driven explosions. Simulations of CCNSe including accurate treatments of neutrino transport and sufficient resolution to capture key instabilities remain among the most expensive numerical simulations in astrophysics, prohibiting large parameter studies in 2D and 3D. Studies spanning a large swath of the incredibly varied initial conditions of CCSNe are possible in 1D, though such simulations must be artificially driven to explode. We present a new method for including the most important effects of convection and turbulence in 1D simulations of neutrino-driven CCSNe, called Supernova Turbulence In Reduced-dimensionality, or STIR. Our new approach includes crucial terms resulting from the turbulent and convective motions of the flow. We estimate the strength of convection and turbulence using a modified mixing-length theory approach, introducing a few free parameters to the model that are fit to the results of 3D simulations. For sufficiently large values of the mixing-length parameter, turbulence-aided neutrino-driven explosions are obtained. We compare the results of STIR to high-fidelity 3D simulations and perform a parameter study of CCSN explosion using 200 solar-metallicity progenitor models from 9 to 120 . We find that STIR is a better predictor of which models will explode in multidimensional simulations than other methods of driving explosions in 1D. We also present a preliminary investigation of predicted observable characteristics of the CCSN population from STIR, such as the distributions of explosion energies and remnant masses.

Simulations of Dynamical Gas–Dust Circumstellar Disks: Going Beyond the Epstein Regime

In circumstellar disks, the size of dust particles varies from submicron to several centimeters, while planetesimals have sizes of hundreds of kilometers. Therefore, various regimes for the aerodynamic drag between solid bodies and gas can be realized in these disks, depending on the grain sizes and velocities: Epstein, Stokes, and Newton, as well as transitional regimes between them. For small bodies moving in the Epstein regime, the time required to establish the constant relative velocity between the gas and bodies can be much less than the dynamical time scale for the problem - the time for the rotation of the disk about the central body. In addition, the dust may be concentrated in individual regions of the disk, making it necessary to take into account the transfer of momentum between the dust and gas. It is shown that, for a system of equations for gas and monodisperse dust, a semi-implicit first-order approximation scheme in time in which the interphase interaction is calculated implicitly, while other forces, such as the pressure gradient and gravity are calculated explicitly, is suitable for stiff problems with intense interphase interactions and for computations of the drag in non-linear regimes. The piece-wise drag coefficient widely used in astrophysical simulations has a discontinuity at some values of the Mach and Knudsen numbers that are realized in a circumstellar disk. A continuous drag coefficient is presented, which corresponds to experimental dependences obtained for various drag regimes.

Magnetic Helicity Dissipation and Production in an Ideal MHD Code

Abstract We study a turbulent helical dynamo in a periodic domain by solving the ideal magnetohydrodynamic (MHD) equations with the FLASH code using the divergence-cleaning eight-wave method and compare our results with direct numerical simulations (DNS) using the Pencil Code. At low resolution, FLASH reproduces the DNS results qualitatively by developing the large-scale magnetic field expected from DNS, but at higher resolution, no large-scale magnetic field is obtained. In all those cases in which a large-scale magnetic field is generated, the ideal MHD results yield too little power at small scales. As a consequence, the small-scale current helicity is too small compared with that of the DNS. The resulting net current helicity has then always the wrong sign, and its statistical average also does not approach zero at late times, as expected from the DNS. Our results have implications for astrophysical dynamo simulations of stellar and galactic magnetism using ideal MHD codes.

Gamow-Teller transitions to Zr93 via the Nb93(t,He3+γ ) reaction at 115 MeV/u and its application to the stellar electron-capture rates

Electron-capture reactions play important roles in the late evolution of core-collapse supernovae. The electron-capture rates used in astrophysical simulations rely on theoretical calculations which have to be tested against and guided by experimental data. We report on the measurement of the Gamow-Teller strength distribution of the odd-mass nucleus $^{93}\mathrm{Nb}$ via the ($t,^{3}\mathrm{He}$ + $\ensuremath{\gamma}$) charge-exchange reaction at a beam energy of 115 MeV/u. The Gamow-Teller strength distributions were extracted up to an excitation energy in $^{93}\mathrm{Zr}$ of 10 MeV. The results were compared with shell-model and quasiparticle random-phase approximation (QRPA) calculations. The theoretical calculations fail to describe the details of the strength distribution, but estimate reasonably well the integrated Gamow-Teller transition strength. Electron-capture rates derived from the measured and theoretical strength distributions match reasonably well, especially at the higher stellar densities of importance for deleptonization during the collapse of the stellar core, since the electron-capture $Q$ value is close to zero and the Fermi energy sufficiently high to ensure that the details of the strength distribution do not have a strong impact on the derived rates. At stellar densities in excess of ${10}^{9}$ g/${\mathrm{cm}}^{3}$, the electron-capture rate based on a single-state approximation used in astrophysical simulations is slightly higher than the rates based on the data and the shell-model and QRPA calculations, likely due to the fact that the approximation includes temperature-dependent effects, which increase the rates. However, the difference is much smaller than that observed in recent studies of nuclei with $Zl40$ near $N=50$, suggesting that the single-state approximation does not account for Pauli-blocking effects for nuclei with $Zl40$ that are much stronger than those for $^{93}\mathrm{Nb}$ with $Z=41$.

Big Data in Astronomy: Surveys, Catalogs, Databases and Archives

We present the modern situation in astronomy, where Big Data coming from the Universe put new tasks for catalogizing, storage, archiving, analysis and usage of the scientific information. The two major characteristics of modern astronomy are multiwavelength (MW) studies (from γ-ray to radio, as well as multi-messenger studies, using also neutrinos, gravitational waves, etc.) and Big Data (including data acquisition, storage and analysis). Present astronomical databases and archives contain billions of objects observed in various wavelengths, both Galactic and extragalactic, and the vast amount of data on them allows new studies and discoveries. Astronomers deal with big numbers. Surveys are the main source for discovery of astronomical objects and accumulation of observational data for further analysis, interpretation, and achieving scientific results. We review the main characteristics of astronomical surveys, we compare photographic and digital eras of astronomical studies (including the development of wide-field observations), we give the present state of MW surveys, and we discuss the Big Data in astronomy and related topics of Virtual Observatories and Computational Astrophysics. The review includes many numbers and data that can be compared to have a possibly overall understanding on the studied Universe, cosmic numbers and their relationship to modern computational possibilities.

Nuclear statistical equilibrium equation of state with a parametrized Dirac–Brückner Hartree–Fock calculation

Abstract We calculate new equations of state (EOSs) for astrophysical simulations in the framework of the extended nuclear statistical equilibrium, in which we minimize the free energy density for the full ensemble of nuclei in a hot and dense stellar environment. To evaluate bulk and surface energies of heavy nuclei and free energies of uniformly distributed nucleons, we use fitting formulae for the interaction energies and single-nucleon potentials at zero temperature of a Dirac–Brückner Hartree–Fock (DBHF) theory, one of the modern approaches to describe homogeneous nuclear matter. We find that the DBHF EOS exhibits larger mass fractions for medium-mass nuclei and smaller mass fractions for the other nuclei than the EOS obtained using the variational method (VM), another modern model for homogeneous nuclear matter. This effect is due to the more deeply bound energy for symmetric nuclear matter and the larger symmetry energy encoded in the DBHF EOS. At supra-nuclear densities, the DBHF EOS exhibits characteristics of a larger free energy, a higher pressure, and a larger neutron chemical potential of neutron-rich matter, which lead to a larger radius of cold neutron stars than that obtained by the VM EOS.

Magritte, a modern software library for 3D radiative transfer: I. Non-LTE atomic and molecular line modelling

ABSTRACT Radiative transfer is a key component in almost all astrophysical and cosmological simulations. We present magritte: a modern open-source software library for 3D radiative transfer. It uses a deterministic ray-tracer and formal solver, i.e. it computes the radiation field by tracing rays through the model and solving the radiative transfer equation in its second-order form along a fixed set of rays originating from each point. magritte can handle structured and unstructured input meshes, as well as smoothed-particle hydrodynamics (SPH) particle data. In this first paper, we describe the numerical implementation, semi-analytic tests and cross-code benchmarks for the non-LTE line radiative transfer module of magritte. This module uses the radiative transfer solver to self-consistently determine the populations of the quantized energy levels of atoms and molecules using an accelerated Lambda iteration (ALI) scheme. We compare magritte with the established radiative transfer solvers ratran (1D) and lime (3D) on the van Zadelhoff benchmark and present a first application to a simple Keplerian disc model. Comparing with lime, we conclude that magritte produces more accurate and more precise results, especially at high optical depth, and that it is faster.

NIHAO-UHD: The properties of MW-like stellar disks in high resolution cosmological simulations

Abstract Simulating thin and extended galactic disks has long been a challenge in computational astrophysics. We introduce the NIHAO-UHD suite of cosmological hydrodynamical simulations of Milky Way mass galaxies and study stellar disk properties such as stellar mass, size and rotation velocity which agree well with observations of the Milky Way and local galaxies. In particular, the simulations reproduce the age-velocity dispersion relation and a multi-component stellar disk as observed for the Milky Way. Half of our galaxies show a double exponential vertical profile, while the others are well described by a single exponential model which we link to the disk merger history. In all cases, mono-age populations follow a single exponential whose scale height varies monotonically with stellar age and radius. The scale length decreases with stellar age while the scale height increases. The general structure of the stellar disks is already set at time of birth as a result of the inside-out and upside-down formation. Subsequent evolution modifies this structure by increasing both the scale length and height of all mono-age populations. Thus, our results put tight constraints on how much dynamical memory stellar disks can retain over cosmological timescales. Our simulations demonstrate that it is possible to form thin galactic disks in cosmological simulations provided there are no significant stellar mergers at low redshifts. Most of the stellar mass is formed in-situ with only a few percent ($\lesssim 5\%$) brought in by merging satellites at early times. Redshift zero snapshots and halo catalogues are publicly available.

Constraints for stellar electron-capture rates on Kr86 via the Kr86(t,He3+γ)Br86 reaction and the implications for core-collapse supernovae

In the late stages of stellar core-collapse, prior to core bounce, electron captures on medium-heavy nuclei drive deleptonization and simulations require the use of accurate reaction rates. Nuclei with neutron number near $N=50$, just above atomic number $Z=28$, play an important role, but rates used in astrophysical simulations rely primarily on a relatively simple single-state approximation. In order to improve the accuracy of astrophysical simulations, experimental data are needed to test the electron-capture rates and to guide the development of better theoretical models. This work presents the results of the $^{86}$Kr($t$,$^{3}$He+$\gamma$) experiment at the NSCL, from which an upper limit for the Gamow-Teller strength up to an excitation energy in $^{86}$Br of 5 MeV is extracted. The derived upper limit for the electron-capture rate on $^{86}$Kr indicates that the rate estimated through the single-state approximation is too high and that rates based on Gamow-Teller strengths estimated in shell-model and QRPA calculations are more accurate. The QRPA calculations tested in this manner were used for estimating the electron capture rates for 78 isotopes near $N=50$ and above $Z=28$. The impact of using these new electron-capture rates in simulations of supernovae instead of the rates based on the single-state approximation is investigated, indicating a significant reduction in the deleptonization that affects multi-messenger signals, such as the emission of neutrinos and gravitational waves.

Machine-learning interpolation of population-synthesis simulations to interpret gravitational-wave observations: A case study

We report on advances to interpret current and future gravitational-wave events in light of astrophysical simulations. A machine-learning emulator is trained on numerical population-synthesis predictions and inserted into a Bayesian hierarchical framework. In this case study, a modest but state-of-the-art suite of simulations of isolated binary stars is interpolated across two event parameters and one population parameter. The validation process of our pipelines highlights how omitting some of the event parameters might cause errors in estimating selection effects, which propagates as systematics to the final population inference. Using LIGO/Virgo data from O1 and O2 we infer that black holes in binaries are most likely to receive natal kicks with one-dimensional velocity dispersion $\sigma$ = 105+44 km/s. Our results showcase potential applications of machine-learning tools in conjunction with population-synthesis simulations and gravitational-wave data.

Akmal-Pandharipande-Ravenhall equation of state for simulations of supernovae, neutron stars, and binary mergers

Differences in the equation of state (EOS) of dense matter translate into differences in astrophysical simulations and their multimessenger signatures. Thus, extending the number of EOSs for astrophysical simulations allows us to probe the effect of different aspects of the EOS in astrophysical phenomena. In this work, we construct the EOS of hot and dense matter based on the Akmal, Pandharipande, and Ravenhall (APR) model and thereby extend the open-source SROEOS code which computes EOSs of hot dense matter for Skyrme-type parametrizations of the nuclear forces. Unlike Skrme-type models, in which parameters of the interaction are fit to reproduce the energy density of nuclear matter and/or properties of heavy nuclei, the EOS of APR is obtained from potentials resulting from fits to nucleon-nucleon scattering and properties of light nuclei. In addition, this EOS features a phase transition to a spin-isospin ordered state of nucleons, termed a neutral pion condensate, at supranuclear densities. We show that differences in the effective masses between EOSs have consequences for the properties of nuclei in the subnuclear inhomogeneous phase of matter. We also test the new EOS of APR in spherically symmetric core-collapse of massive stars with $15\phantom{\rule{0.28em}{0ex}}{M}_{\ensuremath{\bigodot}}$ and $40\phantom{\rule{0.28em}{0ex}}{M}_{\ensuremath{\bigodot}}$, respectively. We find that the phase transition in the EOS of APR speeds up the collapse of the star. However, this phase transition does not generate a second shock wave or another neutrino burst as reported for the hadron-to-quark phase transition. The reason for this difference is that the width of the coexistence region and the latent heat in the EOS of APR are substantially smaller than in the quark-to-hadron transition employed earlier, which results in a significantly smaller softening of the high density EOS.

Preface

Welcome to 2019 9th International Conference on Applied Physics and Mathematics (ICAPM 2019), which will be held in Chulalongkorn University, Bangkok, Thailand during January 21-23, 2019. Chulalongkorn University founded in March 1917 is Thailand’s first institution of higher learning. Chulalongkorn University has 20 faculties, 23 colleges and research institutes, over 8,000 faculty members, and over 37,000 students including undergraduates, postgraduates, and certificate program students. Chulalongkorn University is one of the world’s great universities. We are delighted to come to prestigious Chulalongkorn University to meet with so many of our distinguished collaborators and scientists to explore new knowledge and ideas.ICAPM Conference is one important event organized by American Society for Research (ASR). It has been successfully held in 8 consecutive years since 2011. In the past two years, ICAPM 2017 and ICAPM 2018 Conference Proceedings have been archived into IOP Journal of Physics: Conference Series, Volumes 814 (2017) and 1039 (2018) indexed by ISI Web of Science (Conference Proceedings Citation Index (CPCI), Scopus, Engineering Information (EI), etc. ICAPM 2019 aims to provide a high level international forum which focus on interdisciplinary and multidisciplinary research concerning material analysis and preparation, machinery and manufacturing engineering, fluorescent materials and biological materials, mechatronics and control engineering, metal materials and alloys, applied mathematics and computational modeling, quantum physics and astrophysics, and computer and information technology. These are all fascinating topics related to future needs. 28 Selected and important results will also publish in the peer-reviewed conference journal.We express our thanks and appreciation to our keynote speakers Prof. Yoshihiko Uematsu from Gifu University in Japan, Assoc. Prof. Ratchatin Chancharoen from Chulalongkorn University in Thailand, Prof. Naoyuki Ishimura from Chuo University in Japan, Prof. Jong-Shenq Guo from Tamkang University in Taiwan, Assoc. Prof. Vadim Rashitovich Gasiyarov from South Ural State University in Russia, and all the participants and committee members for all support to ICAPM 2019.January 2019Prof. Po-Liang LiuNational Chung-Hsing University, Taiwan

Thornado-hydro: towards discontinuous Galerkin methods for supernova hydrodynamics11This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of

The toolkit for high-order neutrino-radiation hydrodynamics (thornado) is being developed for simulations of core-collapse supernovae (CCSNe) and related problems. Current capabilities in thornado include solvers for the Euler equations — in non-relativistic and special relativistic limits — and the two-moment model of neutrino transport. The spatial discretization in thornado is based on the discontinuous Galerkin (DG) method, which is receiving increased attention from the computational astrophysics community. In this paper, we provide an overview of the numerical methods for the Euler equations in thornado, and present some encouraging preliminary numerical results from a set of basic tests in one and two spatial dimensions.

Approaching the Black Hole by Numerical Simulations

Black holes represent extreme conditions of physical laws. Predicted about a century ago, they are now accepted as astrophysical reality by most of the scientific community. Only recently has more direct evidence of their existence been found—the detection of gravitational waves from black hole mergers and of the shadow of a supermassive black hole in the center of a galaxy. Astrophysical black holes are typically embedded in an active environment which is affected by the strong gravity. When the environmental material emits radiation, this radiation may carry imprints of the black hole that is hosting the radiation source. In order to understand the physical processes that take place in the close neighborhood of astrophysical black holes, numerical methods and simulations play an essential role. This is simply because the dynamical evolution and the radiative interaction are far too complex in order to allow for an analytic solution of the physical equations. A huge progress has been made over the last decade(s) in the numerical code development, as well as in the computer power that is needed to run these codes. This review tries to summarize the basic questions and methods that are involved in the undertaking of investigating the astrophysics of black holes by numerical means. It is intended for a non-expert audience interested in an overview over this broad field. The review comes along without equations and thus without a detailed expert discussion of the underlying physical processes or numerical specifics. Instead, it intends to illustrate the richness of the field and to motivate further reading. The review puts some emphasis on magneto-hydrodynamic simulations but also touches radiation transfer and merger simulations, in particular pointing out differences in these approaches.

Dual tree traversal on integrated GPUs for astrophysical N-body simulations

In astrophysical N-body simulations, O( N) fast multipole methods (FMMs) with dual tree traversal (DTT) on multi-core CPUs are faster than O( N log N) CPU tree-codes but can still be outperformed by GPU ones. In this article, we aim at combining the best algorithm, namely FMM with DTT, with the most powerful hardware currently available, namely GPUs. In the astrophysical context requiring low accuracies and non-uniform particle distributions, we show that such combination can be achieved thanks to a hybrid CPU-GPU algorithm on integrated GPUs: while the DTT is performed on the CPU cores, the far- and near-field computations are all performed on the GPU cores. We show how to efficiently expose the interactions resulting from the DTT to the GPU cores, how to deploy both the far- and near-field computations on GPU, and how to overlap the parallel DTT on CPU with GPU computations. Based on the falcON code and using OpenCL on AMD Accelerated Processing Units and on Intel integrated GPUs, this first heterogeneous deployment of DTT for FMM outperforms standard multi-core CPUs and matches GPU and high-end CPU performance, being hence more cost- and power-efficient.

Trevr: A generalNlog2Nradiative transfer algorithm

We present TREVR (Tree-based REVerse Ray Tracing), a general algorithm for computing the radiation field, including absorption, in astrophysical simulations. TREVR is designed to handle large numbers of sources and absorbers; it is based on a tree data structure and is thus suited to codes that use trees for their gravity or hydrodynamics solvers (e.g. Adaptive Mesh Refinement). It achieves computational speed while maintaining a specified accuracy via controlled lowering of the resolution of both sources and rays from each source. TREVR computes the radiation field in order ${N\log N_{source}}$ time without absorption and order ${N \log N_{source} \log{N}}$ time with absorption. These scalings arise from merging sources of radiation according to an opening angle criterion and walking the tree structure to trace a ray to a depth that gives the chosen accuracy for absorption. The absorption-depth refinement criterion is unique to TREVR. We provide a suite of tests demonstrating the algorithm's ability to accurately compute fluxes, ionization fronts and shadows.

High-order magnetohydrodynamics for astrophysics with an adaptive mesh refinement discontinuous Galerkin scheme

Modern astrophysical simulations aim to accurately model an ever-growing array of physical processes, including the interaction of fluids with magnetic fields, under increasingly stringent performance and scalability requirements driven by present-day trends in computing architectures. Discontinuous Galerkin methods have recently gained some traction in astrophysics, because of their arbitrarily high order and controllable numerical diffusion, combined with attractive characteristics for high performance computing. In this paper, we describe and test our implementation of a discontinuous Galerkin (DG) scheme for ideal magnetohydrodynamics in the AREPO-DG code. Our DG-MHD scheme relies on a modal expansion of the solution on Legendre polynomials inside the cells of an Eulerian octree-based AMR grid. The divergence-free constraint of the magnetic field is enforced using one out of two distinct cell-centred schemes: either a Powell-type scheme based on nonconservative source terms, or a hyperbolic divergence cleaning method. The Powell scheme relies on a basis of locally divergence-free vector polynomials inside each cell to represent the magnetic field. Limiting prescriptions are implemented to ensure non-oscillatory and positive solutions. We show that the resulting scheme is accurate and robust: it can achieve high-order and low numerical diffusion, as well as accurately capture strong MHD shocks. In addition, we show that our scheme exhibits a number of attractive properties for astrophysical simulations, such as lower advection errors and better Galilean invariance at reduced resolution, together with more accurate capturing of barely resolved flow features. We discuss the prospects of our implementation, and DG methods in general, for scalable astrophysical simulations.

Enhanced Mixing in Giant Impact Simulations with a New Lagrangian Method

Abstract Giant impacts (GIs) are common in the late stage of planet formation. The Smoothed Particle Hydrodynamics (SPH) method is widely used for simulating the outcome of such violent collisions, one prominent example being the formation of the Moon. However, a decade of numerical studies in various areas of computational astrophysics has shown that the standard formulation of SPH suffers from several shortcomings such as artificial surface tension and its tendency to promptly damp turbulent motions on scales much larger than the physical dissipation scale, both resulting in the suppression of mixing. In order to estimate how severe these limitations are when modeling GIs we carried out a comparison of simulations with identical initial conditions performed with the standard SPH as well as with the novel Lagrangian Meshless Finite Mass (MFM) method using the multimethod code, GIZMO. We confirm the lack of mixing between the impactor and target when SPH is employed, while MFM is capable of driving vigorous subsonic turbulence and leads to significant mixing between the two bodies. Modern SPH variants with artificial conductivity, a different formulation of the hydro force or reduced artificial viscosity, do not improve mixing as significantly. Angular momentum is conserved similarly well in both methods, but MFM does not suffer from spurious transport induced by artificial viscosity, resulting in a slightly higher angular momentum of the protolunar disk. Furthermore, SPH initial conditions unphysically smooth the core-mantle boundary, which is easily avoided in MFM.

The challenges of modelling microphysics: ambipolar diffusion, chemistry, and cosmic rays in MHD shocks

From molecular clouds to protoplanetary disks, non-ideal magnetic effects are important in many astrophysical environments. Indeed, in star and disk formation processes, it has become clear that these effects are critical to the evolution of the system. The efficacy of non-ideal effects are, however, determined by the complex interplay between magnetic fields, ionising radiation, cosmic rays, microphysics, and chemistry. In order to understand these key microphysical parameters, we present a one-dimensional non-ideal magnetohydrodynamics code and apply it to a model of a time-dependent, oblique, magnetic shock wave. By varying the microphysical ingredients of the model, we find that cosmic rays and dust play a major role, and that, despite the uncertainties, the inclusion of microphysics is essential to obtain a realistic outcome in magnetic astrophysical simulations.