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ltw public reporting burden foi (Mi collection of information «s estimated to swag* ' nour per response <nrntr1mg the time (or reviewing msttuctinnt Kaarchmg existing data sources gathering and maintaining the data needed, end completing end reviewing the collection o* information. Send comments legerding this ourden eshmeie or any other aspect o' this collection (if information, mclud.ng »ogge*tmn» lor reducing the burden to the Deportment ol Defense fcxecutrve Services end Communicaiions Directorate (0704-01881. Respondent* should be aware th«t nptwithstanding any other proviston ol lew. no person shall be subject to any [wneUv (or f*krtg to comniv with • .-.oBectw of irrformatHm tf it does not thaptey • Current** «eJaj OMB control number
42nd AIAA Plasmadynamics and Lasers Conference, 2011
This paper describes the computer simulation of an ionizing gas passing through a strong shock wave. A program module for solving the fluid dynamics equations for ions, electrons and neutrals, illustrating the effect of charge separation on the flow, is discussed. Previous solution modules in the present effort solved the Navier-Stokes equations, Maxwell"s equations and those for chemical and thermal nonequilibrium. This fourth module completes the set for describing the physics of hypersonic flow of an ionizing gas within an electromagnetic field. Argon gas is used in the present simulation.
Communications of the Byurakan Astrophysical Observatory, 2018
Diffusive shock acceleration (DSA) is a very efficient mechanism of high energy particle acceleration in heliosphere, supernova remnants, stellar winds and gamma-ray bursts. We present microscopic simulation of particle injection and diffusive shock acceleration which is performed with 3D divergence-conserving second-order accurate hybrid code "Maximus". Hydrogen plasma with admixture of various heavy ions is considered. The injection process is found to start through shock reflection for both hydrogen an heavier ions. However, the reflection process depends on charge-to-mass ratio. While hydrogen ions reflection appears at shock ramp and is governed by the cross-shock potential, the reflection of ions with greater A/Z proceeds deeper downstream via gyration in perpendicular magnetic field component. The heavy ions appear to inject into the DSA preferentially, but this chemical enhancement saturates with growing A/Z. The protons injection efficiency is estimated within various approaches, and it is shown that about 20% of initial flow energy goes into accelerated particles.
Journal of Computational Physics, 2005
A two-dimensional (2D) visual computer code to solve the steady state (SS) or transient shock problems including partially ionizing plasma is presented. Since the flows considered are hypersonic and the resulting temperatures are high, the plasma is partially ionized. Hence the plasma constituents are electrons, ions and neutral atoms. It is assumed that all the above species are in thermal equilibrium, namely, that they all have the same temperature. The ionization degree is calculated from Saha equation as a function of electron density and pressure by means of a nonlinear Newton type root finding algorithms. The code utilizes a wave model and numerical fluctuation distribution (FD) scheme that runs on structured or unstructured triangular meshes. This scheme is based on evaluating the mesh averaged fluctuations arising from a number of waves and distributing them to the nodes of these meshes in an upwind manner. The physical properties (directions, strengths, etc.) of these wave patterns are obtained by a new wave model: ION-A developed from the eigen-system of the flux Jacobian matrices. Since the equation of state (EOS) which is used to close up the conservation laws includes electronic effects, it is a nonlinear function and it must be inverted by iterations to determine the ionization degree as a function of density and temperature. For the time advancement, the scheme utilizes a multistage Runge-Kutta (RK) algorithm with time steps carefully evaluated from the maximum possible propagation speed in the solution domain. The code runs interactively with the user and allows to create different meshes to use different initial and boundary conditions and to see changes of desired physical quantities in the form of color and vector graphics. The details of the visual properties of the code has been published before (see [N. Aslan, A visual fluctuation splitting scheme for magneto-hydrodynamics with a new sonic fix and Euler limit, J. Comput. Phys. 197 (2004) 1-27]). The two-dimensional nature of ION-A was presented by a planar shock wave propagating over a circular obstacle. It was demonstrated that including the effects of ionization in calculating complex flows is important, even when they appear initially negligible. This code can be used to accurately simulate the nonlinear time dependent evolution of neutral or ionized plasma flows from supersonic to hypersonic regimes.
Fluid Dynamics Conference, 1996
IEEE Transactions on Plasma Science, 2000
Journal of Physics: Conference Series, 2008
We present the simulations of two relevant hydrodynamical problems related to astrophysical phenomena performed by three different codes. The numerical results from these codes will be compared in order to test both the numerical method implemented inside them and the influence of the physical phenomena simulated by the codes. Under some conditions laser produced plasmas could be scaled to the typical conditions prevailing in astrophysical plasmas. Therefore, such similarity allows to use existing laser facilities and numerical codes suitable to a laser plasma regime, for studying astrophysical proccesses. The codes are the radiation fluid dynamic 2D ARWEN code and the 3D HERACLES, and, without radiation energy transport, a Smoothed-Particle Hydrodynamics (SPH) code. These codes use different numerical techniques and have overlapping range of application, from laser produced plasmas to astrophysical plasmas. We also present the first laser experiments obtaining cumulative jets with a velocity higher than 100 km/s.
Physics of Plasmas, 2015
Hypervelocity particles, such as meteoroids and space debris, routinely impact spacecraft and are energetic enough to vaporize and ionize themselves and as well as a portion of the target material. The resulting plasma rapidly expands into the surrounding vacuum. While plasma measurements from hypervelocity impacts have been made using ground-based technologies such as light gas guns and Van de Graaff dust accelerators, some of the basic plasma properties vary significantly between experiments. There have been both ground-based and in-situ measurements of radio frequency (RF) emission from hypervelocity impacts, but the physical mechanism responsible and the possible connection to the impact-produced plasma are not well understood. Under certain conditions, the impact-produced plasma can have deleterious effects on spacecraft electronics by providing a new current path, triggering an electrostatic discharge, causing electromagnetic interference, or generating an electromagnetic pulse. Multi-physics simulations of plasma production from hypervelocity impacts are presented. These simulations incorporate elasticity and plasticity of the solid target, phase change and plasma formation, and non-ideal plasma physics due to the high density and low temperature of the plasma. A smoothed particle hydrodynamics method is used to perform a continuum dynamics simulation with these additional physics. By examining a series of hypervelocity impacts, basic properties of the impact produced plasma plume (density, temperature, expansion speed, charge state) are determined for impactor speeds between 10 and 72 km/s. For a large range of higher impact speeds (30-72 km/s), we find the temperature is unvarying at 2.5 eV. We also find that the plasma plume is weakly ionized for impact speeds less than 14 km/s and fully ionized for impact speeds greater than 20 km/s, independent of impactor mass. This is the same velocity threshold for the detection of RF emission in recent Van de Graaff experiments, suggesting that the RF is correlated to the formation of fully ionized plasma. V
model parameters for different dimensionality. Most current burn models do not accurately predict both one-dimensional plate acceleration experiments and two-dimensional cylinder expansion experiments simultaneously. Our implementation is significant because it represents the first time a multi-dimensiona l model has been used to successfully predict multi-dimensiona l detonation effects without requiring a modification of the model parameters. Examples of the features of CTH will be given. The emphasis in simulations shown will be in compar- ison with well characterized experiments covering key
Advances in Space Research, 1984
Brief overview of previous studies of ion thermalization at the shock transition is given. One non-quite typical Prognoz-8 quasi-perpendicular bow shock crossing on 11 February 1981 is considered for which high-time resolution data on plasma and ELF electric field fluctuations are available. Strong turbulence in LH-raage that is associated with two-stream ion motion upstream of shock transition is characterized by an exponential growth and saturation of these fluctuations at a level of '~'1O0mV/zn. The heating of ions at the main shock transition is associated with pulse-like increase of these waves amplitude. Relaxation of gyrating beams downstream of the main shock transition appears to be associated with ion-cyclotrG.n waves and additional heating of ions and passes through two phases: h~ydrodynaznic and kinetic ones. Linear and time scales of the events are estimated.
"Arts" Special Issue. Kathlyn Cooney, Alisée Devillers (eds.), Ancient Egyptian Art Studies: Art in Motion, a Social Tool of Power and Resistance, 2024
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Proceedings of the Prehistoric Society, 1973
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Journal of Functional Morphology and Kinesiology