scholarly journals Magnetohydrodynamic Ionizing Shock Waves in a Conducting Medium

1965 ◽  
Vol 18 (4) ◽  
pp. 363 ◽  
Author(s):  
B Green ◽  
RM May
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Shock Waves ◽  
Field Strength ◽  
Shock Front ◽  
Ionization Energy ◽  
Conducting Medium ◽  
Flow Parameters ◽  
Magnetohydrodynamic Shock ◽  
Initial Magnetic Field

We present numerical calculations for the flow parameters (velocity, density, pressure, etc.) in a magnetohydrodynamic shock wave propagating in a conducting medium. The effect of ionization in the shock front is included. The results are presented graphically for a complete range of the initial magnetic field strength and direction, and for several arbitrary values of the ionization energy of the downstream fluid.

The structure of magneto-hydrodynamic shock waves

1955 ◽  
Vol 233 (1194) ◽  
pp. 367-376 ◽  
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Shock Waves ◽  
Shock Front ◽  
Critical Value ◽  
Detailed Structure ◽  
Wide Region ◽  
Special Cases ◽  
Field Velocity ◽  
Initial Magnetic Field

The equations describing the detailed structure of magneto-hydrodynamic shocks are derived and their solutions discussed in the special cases of high or low electrical conductivity. For high conductivity the shock front has a width of several mean free paths. For low conductivity, if the initial magnetic field is smaller than a certain critical value, a sharp shock is preceded by a wide region in which the field, velocity and temperature change slowly; if the field is larger than this critical value, then no sharp shock occurs and all the variables change slowly over a wide region. A small double layer of charge is built up on the shock front as a result of the Hall effect.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

Mechanism analysis of magnetohydrodynamic shock control in hypersonic flow

2021 ◽  
pp. 095441002110425
Author(s):  
Shichao Luo ◽  
Jun Liu ◽  
Hao Jiang ◽  
Junyuan Wang
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Oblique Shock ◽  
Mechanism Analysis ◽  
Dipole Magnet ◽  
Counter Flow ◽  
Shock Control ◽  
Magnetohydrodynamic Shock

The effects of external magnetic fields on the shock-wave configuration at hypersonic plasma flow field are investigated in this paper. A series of numerical simulations over various geometry configurations, namely, a blunt body and a fixed-geometry inlet forebody, have been conducted by varying the applied magnetic field under different freestream conditions. Results show that magnetohydrodynamic shock control capabilities under three types of magnetic field are ranked from weak to strong as dipole magnet, solenoid magnet, and uniform magnet field. Under the same applied magnetic field, it is easier to deflect the shock at a relatively high altitude condition, compared with the low altitude case. The bow shock standoff distance is dependent on the distribution of counter-flow Lorentz force right after shock in the stagnation region. For the oblique shock control, the function of two components of Lorentz force is different that the counter-flow one decelerates the flow and increases the shock-wave angle, while the normal one squeezes the oblique shock and deflects the streamlines.

scholarly journals Relativistic Particle Acceleration in Plerions

1994 ◽  
Vol 142 ◽  
pp. 797-806
Author(s):  
Jonathan Arons ◽  
Marco Tavani
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Waves ◽  
Shock Front ◽  
Heavy Ions ◽  
Surface Brightness ◽  
Crab Nebula ◽  
Electrons And Positrons ◽  
The Crab Nebula ◽  
The Magnetic Field

AbstractWe discuss recent research on the structure and particle acceleration properties of relativistic shock waves in which the magnetic field is transverse to the flow direction in the upstream medium, and whose composition is either pure electrons and positrons or primarily electrons and positrons with an admixture of heavy ions. Particle-in-cell simulation techniques as well as analytic theory have been used to show that such shocks in pure pair plasmas are fully thermalized—the downstream particle spectra are relativistic Maxwellians at the temperature expected from the jump conditions. On the other hand, shocks containing heavy ions which are a minority constituent by number but which carry most of the energy density in the upstream medium do put ~20% of the flow energy into a nonthermal population of pairs downstream, whose distribution in energy space is N(E) ∝ E−2, where N(E)dE is the number of particles with energy between E and E + dE.The mechanism of thermalization and particle acceleration is found to be synchrotron maser activity in the shock front, stimulated by the quasi-coherent gyration of the whole particle population as the plasma flowing into the shock reflects from the magnetic field in the shock front. The synchrotron maser modes radiated by the heavy ions are absorbed by the pairs at their (relativistic) cyclotron frequencies, allowing the maximum energy achievable by the pairs to be γ±m±c2 = mic2γ1/Zi, where γ1 is the Lorentz factor of the upstream flow and Zi, is the atomic number of the ions. The shock’s spatial structure is shown to contain a series of “overshoots” in the magnetic field, regions where the gyrating heavy ions compress the magnetic field to levels in excess of the eventual downstream value.This shock model is applied to an interpretation of the structure of the inner regions of the Crab Nebula, in particular to the “wisps,” surface brightness enhancements near the pulsar. We argue that these surface brightness enhancements are the regions of magnetic overshoot, which appear brighter because the small Larmor radius pairs are compressed and radiate more efficiently in the regions of more intense magnetic field. This interpretation suggests that the structure of the shock terminating the pulsar’s wind in the Crab Nebula is spatially resolved, and allows one to measure γ1, and a number of other properties of the pulsar’s wind. We also discuss applications of the shock theory to the termination shocks of the winds from rotation-powered pulsars embedded in compact binaries. We show that this model adequately accounts for (and indeed predicted) the recently discovered X-ray flux from PSR 1957+20, and we discuss several other applications to other examples of these systems.Subject headings: acceleration of particles — ISM: individual (Crab Nebula) — relativity — shock waves

scholarly journals On Fast Magnetic Field Reconnection

1976 ◽  
Vol 71 ◽  
pp. 353-366 ◽  
Author(s):  
E. R. Priest ◽  
A. M. Soward
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Electrical Conductivity ◽  
Shock Waves ◽  
Similarity Solutions ◽  
Diffusion Region ◽  
Magnetohydrodynamic Equations ◽  
Reconnection Rate ◽  
Mathematical Basis ◽  
Rate Dependent

The first model for ‘fast’ magnetic field reconnection at speeds comparable with the Alfvén speed was put forward by Petschek (1964). It involves one shock wave in each quadrant radiating from a central diffusion region and leads to a maximum reconnection rate dependent on the electrical conductivity but typically of order 10-1 or 10-2 of the Alfvén speed. Sonnerup (1970) and Yeh and Axford (1970) then looked for similarity solutions of the magnetohydrodynamic equations, valid at large distances from the diffusion region; by contrast with Petschek's analysis, their models have two waves in each quadrant and produce no sub-Alfvénic limit on the reconnection rate.Our approach has been, like Yeh and Axford, to look for solutions valid far from the diffusion region, but we allow only one wave in each quadrant, since the second is externally generated and so unphysical for astrophysical applications. The result is a model which qualitatively supports Petschek's picture; in fact it can be regarded as putting Petschek's model on a firm mathematical basis. The differences are that the shock waves are curved rather than straight and the maximum reconnection rate is typically a half of what Petschek gave. The paper is a summary of a much larger one (Soward and Priest, 1976).

scholarly journals A Self-Similar Flow behind a Magnetogasdynamic Shock Wave Generated by a Moving Piston in a Gravitating Gas with Variable Density: Isothermal Flow

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
G. Nath ◽  
A. K. Sinha
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Ambient Medium ◽  
Initial Density ◽  
Power Laws ◽  
Variable Density ◽  
Ideal Gas ◽  
Piston Velocity ◽  
Azimuthal Magnetic Field ◽  
Initial Magnetic Field

The propagation of a cylindrical (or spherical) shock wave in an ideal gas with azimuthal magnetic field and with or without self-gravitational effects is investigated. The shock wave is driven out by a piston moving with time according to power law. The initial density and the initial magnetic field of the ambient medium are assumed to be varying and obeying power laws. Solutions are obtained, when the flow between the shock and the piston is isothermal. The gas is assumed to have infinite electrical conductivity. The shock wave moves with variable velocity, and the total energy of the wave is nonconstant. The effects of variation of the piston velocity exponent (i.e., variation of the initial density exponent), the initial magnetic field exponent, the gravitational parameter, and the Alfven-Mach number on the flow field are obtained. It is investigated that the self-gravitation reduces the effects of the magnetic field. A comparison is also made between gravitating and nongravitating cases.

Magneto-gasdynamic flow over a wedge

1966 ◽  
Vol 25 (1) ◽  
pp. 165-178 ◽  
Author(s):  
D. C. Pack ◽  
G. W. Swan
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Shock Waves ◽  
Wave Pattern ◽  
Ionized Gas ◽  
Current Sheets ◽  
Gasdynamic Flow ◽  
The Stability ◽  
The Magnetic Field ◽  
Insight Into

The solution for the flow of a fully ionized gas over a wedge of finite angle is known for the case when the applied magnetic field is aligned with the incident stream. In this flow there are current sheets on the surfaces of the wedge. When the magnetic field is allowed to deviate slightly from the stream, the current sheets may move into the gas and become shock waves. The magnetic fields adjacent to the wedge above and below it have to be matched. A perturbation method is introduced by means of which expressions for the unknown quantities in the different regions may be determined when there are four shocks attached to the wedge. The results give insight into the manner in which the shock-wave pattern develops as the obliquity of the magnetic field to the stream increases. The question of the stability of the shock waves is also examined.

scholarly journals Propagation of Shock Waves in a Polytrope with a Toroidal Magnetic Field. II. Solution of Complete Differential Equations

1969 ◽  
Vol 22 (5) ◽  
pp. 605
Author(s):  
NK Sinha
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Shock Waves ◽  
Differential Equations ◽  
Toroidal Magnetic Field ◽  
Initial Values ◽  
Made In

The differential equations for the shock parameters along shock rays in the case of propagation of a spherically developed shock wave in a polytrope with a toroidal magnetic field, obtained in Part I, have been integrated numerically for a particular set of initial values. The results are compared with the corresponding results in Part I obtained by neglecting certain small terms and it is found that the effect of this omission is not significant. This substantiates the results and justifies the simplification made in Part 1.

scholarly journals Propagation of Shock Waves in a Polytrope with a Toroidal Magnetic Field. I. Simplified Solution of Differential Equations

1969 ◽  
Vol 22 (5) ◽  
pp. 589
Author(s):  
NK Sinha
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Approximate Solution ◽  
Partial Differential Equations ◽  
Shock Waves ◽  
Differential Equations ◽  
Toroidal Magnetic Field ◽  
Spherical Shock Wave ◽  
Simplified Solution ◽  
Spherical Shock

The propagation of an initially spherical shock wave in a polytrope with a magnetic field has been studied. The model chosen for the purpose was that of a poly trope with a toroidal magnetic field given previously by Sinha. Butler's method has been extended to transform the set of governing partial differential equations into a set of ordinary differential equations involving derivatives in the direction of propagation of the shock element at any point. An approximate solution is obtained and the effect of the toroidal magnetic field on the geometry of the front as well as on the effects brought about by the shock is discussed.

scholarly journals Shock Waves Propagation in the Turbulent Interplanetary Plasma

1996 ◽  
Vol 154 ◽  
pp. 23-28
Author(s):  
I.V. Chashei ◽  
V.I. Shishov
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Shock Front ◽  
Interplanetary Shock ◽  
Energy Losses ◽  
Strong Turbulence ◽  
Background Turbulence ◽  
Interplanetary Plasma ◽  
Waves Propagation

AbstractEffect of turbulence on interplanetary shock waves propagation is considered. It is shown that background turbulence results in the additional shock wave deceleration which may be comparable with the deceleration due to plasma sweeping. The turbulent deceleration is connected with the energy losses due to the strong turbulence amplification behind the moving shock front.

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