scholarly journals Analysis of microscopic properties of radiative shock experiments performed at the Orion laser facility

2018 ◽  
Vol 6 ◽  
Author(s):  
R. Rodríguez ◽  
G. Espinosa ◽  
J. M. Gil ◽  
F. Suzuki-Vidal ◽  
T. Clayson ◽  
...  
Keyword(s):  
Spectroscopic Properties ◽  
Radiation Hydrodynamics ◽  
Post Processing ◽  
Radiative Shock ◽  
Hydrodynamic Simulations ◽  
Shock Region ◽  
Laser Facility ◽  
Post Shock ◽  
Charge State Distributions ◽  
Thermodynamic Regime

In this work we have conducted a study on the radiative and spectroscopic properties of the radiative precursor and the post-shock region from experiments with radiative shocks in xenon performed at the Orion laser facility. The study is based on post-processing of radiation-hydrodynamics simulations of the experiment. In particular, we have analyzed the thermodynamic regime of the plasma, the charge state distributions, the monochromatic opacities and emissivities, and the specific intensities for plasma conditions of both regions. The study of the intensities is a useful tool to estimate ranges of electron temperatures present in the xenon plasma in these experiments and the analysis performed of the microscopic properties commented above helps to better understand the intensity spectra. Finally, a theoretical analysis of the possibility of the onset of isobaric thermal instabilities in the post-shock has been made, concluding that the instabilities obtained in the radiative-hydrodynamic simulations could be thermal ones due to strong radiative cooling.

scholarly journals Target Design for XUV Probing of Radiative Shock Experiments

2020 ◽  
Vol 6 (1) ◽  
pp. 30-41
Author(s):  
U. Chaulagain ◽  
C. Stehlé ◽  
P. Barroso ◽  
M. Kozlova ◽  
J. Nejdl ◽  
...  
Keyword(s):  
Laboratory Astrophysics ◽  
The Novel ◽  
Radiative Shock ◽  
Radiative Shocks ◽  
Numerical Studies ◽  
Laser Facility ◽  
Post Shock ◽  
Technical Specifications ◽  
Novel Design ◽  
Target Design

Radiative shocks are strong shocks characterized by plasma at a high temperature emitting an important fraction of its energy as radiation. Radiative shocks are commonly found in many astrophysical systems and are templates of radiative hydrodynamic flows, which can be studied experimentally using high-power lasers. This is not only important in the context of laboratory astrophysics but also to benchmark numerical studies. We present details on the design of experiments on radiative shocks in xenon gas performed at the kJ scale PALS laser facility. It includes technical specifications for the tube targets design and numerical studies with the 1-D radiative hydrodynamics code MULTI. Emphasis is given to the technical feasibility of an XUV imaging diagnostic with a 21 nm (~58 eV) probing beam, which allows to probe simultaneously the post-shock and the precursor region ahead of the shock. The novel design of the target together with the improved X-ray optics and XUV source allow to show both the dense post-shock structure and the precursor of the radiative shock.

scholarly journals Effects of radiation in accretion regions of classical T Tauri stars

2019 ◽  
Vol 629 ◽  
pp. L9 ◽  
Author(s):  
S. Colombo ◽  
L. Ibgui ◽  
S. Orlando ◽  
R. Rodriguez ◽  
G. Espinosa ◽  
...  
Keyword(s):  
Thermal Conduction ◽  
Thermal Structure ◽  
Radiation Hydrodynamics ◽  
Shock Heating ◽  
T Tauri ◽  
Shock Region ◽  
Accretion Rates ◽  
Post Shock ◽  
Effects Of Radiation ◽  
The Impact

Context. Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns where optically thin and thick plasma components coexist. Thus, an accurate description of these impacts is necessary to account for the effects of absorption and emission of radiation. Aims. We study the effects of radiation emerging from shock-heated plasma in impact regions on the structure of the pre-shock down-falling material. We investigate whether a significant absorption of radiation occurs and if it leads to a pre-shock heating of the accreting gas. Methods. We developed a radiation hydrodynamics model describing an accretion column impacting onto the surface of a classical T Tauri star. The model takes into account the stellar gravity, the thermal conduction, and the effects of radiative losses and of absorption of radiation by matter in the nonlocal thermodynamic equilibrium regime. Results. After the impact, a hot slab of post-shock plasma develops at the base of the accretion column. Part of the radiation emerging from the slab is absorbed by the pre-shock accreting material. As a result, the pre-shock accretion column gradually heats up to temperatures of 105 K, forming a radiative precursor of the shock. The precursor has a thermal structure with the hottest part at T ≈ 105 K, with a size comparable to that of the hot slab, above the post-shock region. At larger distances the temperature gradually decreases to T ≈ 104 K. Conclusions. Our model predicts that ≈70% of the radiation emitted by the post-shock plasma is absorbed by the pre-shock accretion column immediately above the slab and is re-emitted in the UV band. This may explain why accretion rates derived from UV observations are systematically higher than rates inferred from X-ray observations.

scholarly journals Characterization of laser-driven Radiative shock of Astrophysical interests

2015 ◽  
Vol 11 (A29A) ◽  
Author(s):  
U. Chaulagain ◽  
C. Stehlé ◽  
J. Larour ◽  
M. Kozlová ◽  
F. Suzuki-Vidal ◽  
...  
Keyword(s):  
Shock Waves ◽  
Shock Structure ◽  
Experimental Results ◽  
Radiative Shock ◽  
X Ray ◽  
Laser Facility ◽  
Post Shock

AbstractWe highlight the recent experimental results on laser-driven radiative shock waves of astrophysical interests using kJ PALS laser facility. The generated shock is probed instantaneously by X-ray laser (λ = 21.2 nm) showing an unambiguous shock structure that includes both the post-shock and the precursor.

scholarly journals 2D numerical study for magnetic field dependence of neutrino-driven core-collapse supernova models

2020 ◽  
Vol 499 (3) ◽  
pp. 4174-4194
Author(s):  
J Matsumoto ◽  
T Takiwaki ◽  
K Kotake ◽  
Y Asahina ◽  
H R Takahashi
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Small Scale ◽  
Radiation Hydrodynamics ◽  
Initial Strength ◽  
Shock Region ◽  
Main Driver ◽  
Post Shock ◽  
The Magnetic Field ◽  
Initial Magnetic Field

ABSTRACT We study the effects of the magnetic field on the dynamics of non-rotating stellar cores by performing 2D, magnetohydrodynamic (MHD) simulations. To this end, we have updated our neutrino-radiation-hydrodynamics supernova code to include MHD employing a divergence cleaning method with both careful treatments of finite volume and area reconstructions. By changing the initial strength of the magnetic field, the evolution of 15.0, 18.4, and $27.0\,\rm M_\odot$ pre-supernova progenitors is investigated. An intriguing finding in our study is that the neutrino-driven explosion occurs regardless of the strength of the initial magnetic field. For the 2D models presented in this work, the neutrino heating is the main driver for the explosion, whereas the magnetic field secondary contributes to the pre-explosion dynamics. Our results show that the strong magnetic field weakens the growth of the neutrino-driven turbulence in the small scale compared to the weak magnetic field. This results in the slower increase of the turbulent kinetic energy in the post-shock region, leading to the slightly delayed onset of the shock revival for models with the stronger initial magnetic field.

scholarly journals Super-luminous Type II supernovae powered by magnetars

2018 ◽  
Vol 613 ◽  
pp. A5 ◽  
Author(s):  
Luc Dessart ◽  
Edouard Audit
Keyword(s):  
Light Curve ◽  
Spectroscopic Properties ◽  
Radiation Hydrodynamics ◽  
Equal Proportion ◽  
Type Ii ◽  
Standard Type ◽  
Fluid Instabilities ◽  
Dense Shell ◽  
Standard Energy ◽  
Photospheric Temperature

Magnetar power is believed to be at the origin of numerous super-luminous supernovae (SNe) of Type Ic, arising from compact, hydrogen-deficient, Wolf-Rayet type stars. Here, we investigate the properties that magnetar power would have on standard-energy SNe associated with 15–20 M⊙ supergiant stars, either red (RSG; extended) or blue (BSG; more compact). We have used a combination of Eulerian gray radiation-hydrodynamics and non-LTE steady-state radiative transfer to study their dynamical, photometric, and spectroscopic properties. Adopting magnetar fields of 1, 3.5, 7 × 1014 G and rotational energies of 0.4, 1, and 3 × 1051 erg, we produce bolometric light curves with a broad maximum covering 50–150 d and a magnitude of 1043–1044 erg s−1. The spectra at maximum light are analogous to those of standard SNe II-P but bluer. Although the magnetar energy is channelled in equal proportion between SN kinetic energy and SN luminosity, the latter may be boosted by a factor of 10–100 compared to a standard SN II. This influence breaks the observed relation between brightness and ejecta expansion rate of standard Type II SNe. Magnetar energy injection also delays recombination and may even cause re-ionization, with a reversal in photospheric temperature and velocity. Depositing the magnetar energy in a narrow mass shell at the ejecta base leads to the formation of a dense shell at a few 1000 km s−1, which causes a light-curve bump at the end of the photospheric phase. Depositing this energy over a broad range of mass in the inner ejecta, to mimic the effect of multi-dimensional fluid instabilities, prevents the formation of a dense shell and produces an earlier-rising and smoother light curve. The magnetar influence on the SN radiation is generally not visible prior to 20–30 d, during which one may discern a BSG from a RSG progenitor. We propose a magnetar model for the super-luminous Type II SN OGLE-SN14-073.

scholarly journals Balmer-dominated shocks in Tycho’s SNR: omnipresence of CRs

2017 ◽  
Vol 12 (S331) ◽  
pp. 248-253
Author(s):  
Sladjana Knežević ◽  
Ronald Läsker ◽  
Glenn van de Ven ◽  
Joan Font ◽  
John C. Raymond ◽  
...  
Keyword(s):  
Line Width ◽  
Cosmic Ray ◽  
Wide Field ◽  
Hydrogen Atoms ◽  
Narrow Line Width ◽  
Shock Region ◽  
Bayesian Evidence ◽  
Post Shock ◽  
Spurious Result ◽  
First Time

AbstractWe present wide-field, spatially and highly resolved spectroscopic observations of Balmer filaments in the northeastern rim of Tycho’s supernova remnant in order to investigate the signal of cosmic-ray (CR) acceleration. The spectra of Balmer-dominated shocks (BDSs) have characteristic narrow (FWHM ~ 10 km s−1) and broad (FWHM ~ 1000 km s−1) Hα components. CRs affect the Hα-line parameters: heating the cold neutrals in the interstellar medium results in broadening of the narrow Hα-line width beyond 20 km s−1, but also in reduction of the broad Hα-line width due to energy being removed from the protons in the post-shock region. For the first time we show that the width of the narrow Hα line, much larger than 20 km s−1, is not a resolution or geometric effect nor a spurious result of a neglected intermediate (FWHM ~ 100 km s−1) component resulting from hydrogen atoms undergoing charge exchange with warm protons in the broad-neutral precursor. Moreover, we show that a narrow line width ≫ 20 km s−1extends across the entire NE rim, implying CR acceleration is ubiquitous, and making it possible to relate its strength to locally varying shock conditions. Finally, we find several locations along the rim, where spectra are significantly better explained (based on Bayesian evidence) by inclusion of the intermediate component, with a width of 180 km s−1on average.

scholarly journals Clumping of ejecta and accelerated cosmic rays in the evolution of type Ia SNRs

2013 ◽  
Vol 9 (S296) ◽  
pp. 397-398
Author(s):  
S. Orlando ◽  
F. Bocchino ◽  
M. Miceli ◽  
O. Petruk ◽  
M. L. Pumo
Keyword(s):  
Cosmic Rays ◽  
Supernova Remnant ◽  
Contact Discontinuity ◽  
Back Reaction ◽  
Shock Region ◽  
Model Predictions ◽  
Type Ia ◽  
Forward Shock ◽  
Post Shock ◽  
Mhd Modeling

AbstractWe investigate the role played by initial clumping of ejecta and by efficient acceleration of cosmic rays (CRs) in determining the density structure of the post-shock region of a Type Ia supernova remnant (SNR) through detailed 3D MHD modeling. Our model describes the expansion of a SNR through a magnetized interstellar medium (ISM), including the initial clumping of ejecta and the effects on shock dynamics due to back-reaction of accelerated CRs. The model predictions are compared to the observations of SN 1006. We found that the back-reaction of accelerated CRs alone cannot reproduce the observed separation between the forward shock (FS) and the contact discontinuity (CD) unless the energy losses through CR acceleration and escape are very large and independent of the obliquity angle. On the contrary, the clumping of ejecta can naturally reproduce the observed small separation and the occurrence of protrusions observed in SN 1006, even without the need of accelerated CRs. We conclude that FS-CD separation is a probe of the ejecta structure at the time of explosion rather than a probe of the efficiency of CR acceleration in young SNRs.

scholarly journals Effects of Lower Boundary Conditions on the Stability of Radiative Shocks

2002 ◽  
Vol 19 (2) ◽  
pp. 282-292 ◽  
Author(s):  
Curtis J. Saxton
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Lower Boundary ◽  
Stationary Flow ◽  
Physical Models ◽  
Lower Boundary Condition ◽  
Stability Properties ◽  
Shock Region ◽  
Post Shock ◽  
The Stability

AbstractThermal instabilities can cause a radiative shock to oscillate, thereby modulating the emission from the post-shock region. The mode frequencies are approximately quantised in analogy to those of a vibrating pipe. The stability properties depend on the cooling processes, the electron–ion energy exchange, and the boundary conditions. This paper considers the effects of the lower boundary condition on the post-shock flow, both ideally and for some specific physical models. Specific cases include constant perturbed velocity, pressure, density, flow rate, or temperature at the lower boundary, and the situation with nonzero stationary flow velocity at the lower boundary. It is found that for cases with zero terminal stationary velocity, the stability properties are insensitive to the perturbed hydrodynamic variables at the lower boundary. The luminosity responses are generally dependent on the lower boundary condition.

scholarly journals Cooling and instabilities in colliding flows

2021 ◽  
Author(s):  
R N Markwick ◽  
A Frank ◽  
J Carroll-Nellenback ◽  
B Liu ◽  
E G Blackman ◽  
...  
Keyword(s):  
Thermal Instability ◽  
Three Dimensional ◽  
Oscillation Period ◽  
Three Dimensions ◽  
Temperature Dependent ◽  
Radiative Shock ◽  
Hydrodynamic Simulations ◽  
Protostellar Jets ◽  
The One ◽  
Cooling Function

Abstract Collisional self-interactions occurring in protostellar jets give rise to strong shocks, the structure of which can be affected by radiative cooling within the flow. To study such colliding flows, we use the AstroBEAR AMR code to conduct hydrodynamic simulations in both one and three dimensions with a power law cooling function. The characteristic length and time scales for cooling are temperature dependent and thus may vary as shocked gas cools. When the cooling length decreases sufficiently rapidly the system becomes unstable to the radiative shock instability, which produces oscillations in the position of the shock front; these oscillations can be seen in both the one and three dimensional cases. Our simulations show no evidence of the density clumping characteristic of a thermal instability, even when the cooling function meets the expected criteria. In the three-dimensional case, the nonlinear thin shell instability (NTSI) is found to dominate when the cooling length is sufficiently small. When the flows are subjected to the radiative shock instability, oscillations in the size of the cooling region allow NTSI to occur at larger cooling lengths, though larger cooling lengths delay the onset of NTSI by increasing the oscillation period.

scholarly journals Colliding stellar winds: X-ray emission and instabilities

1995 ◽  
Vol 163 ◽  
pp. 486-494
Author(s):  
Ian R. Stevens
Keyword(s):  
Stellar Winds ◽  
Radiation Hydrodynamics ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Radiation Fields ◽  
Basic Physics ◽  
Hydrodynamic Calculations ◽  
Basic Characteristics ◽  
Colliding Winds ◽  
Insight Into

Colliding stellar winds are an important part of early-type binaries. In this paper I discuss the phenomenon, concentrating mainly on the basic hydrodynamics of colliding winds, and the physics of X-ray emission. The following topics are covered:1) Basic physics: The basic characteristics of the shock-produced thermal X-ray emission, and discuss general trends of X-ray emission from colliding wind binaries (CWBs).2) Hydrodynamic simulations: Recent calculations have found that the interface in colliding winds is usually dynamically unstable, with three distinct instabilities.3) Gamma Velorum: recent ROSAT observations give much insight into colliding winds. I discuss recent hydrodynamic calculations pertaining to these observations.4) Radiation Hydrodynamics in CWBs: Recent calculations have included the effects of both radiation fields on the wind hydrodynamics in colliding wind systems.

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