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Showing papers on "Shock wave published in 1981"


Journal ArticleDOI
TL;DR: The proceedings of EXPLOMET 90, the International Conference on the Materials Effects of Shock-Wave and High-Strain-Rate Phenomena, held August 1990, in La Jolla, California, represent a global and up-to-date appraisal of this field as discussed by the authors.
Abstract: These proceedings of EXPLOMET 90, the International Conference on the Materials Effects of Shock-Wave and High-Strain-Rate Phenomena, held August 1990, in La Jolla, California, represent a global and up-to-date appraisal of this field. Contributions (more than 100) deal with high-strain-rate deforma

852 citations


Journal ArticleDOI
TL;DR: In this article, measurements from the Lepedea plasma instruments and the flux gate magnetometers on ISEE 1 and 2 are used to examine the nature of the hydromagnetic waves associated with the various classes of ions backstreaming from the earth's bow shock.
Abstract: Measurements from the Lepedea plasma instruments and the flux gate magnetometers on ISEE 1 and 2 are used to examine the nature of the hydromagnetic waves associated with the various classes of ions backstreaming from the earth's bow shock. The reflected ions, which are confined to a narrow energy and angular range, are accompanied by small amplitude (less than approximately 1/2 gamma peak to peak) left-handed waves at frequencies close to 1 Hz in the spacecraft frame. Diffuse backstreaming particles with a broad energy spectrum are associated with low frequency (approximately 30-s period), large amplitude (approximately 5 gamma peak to peak) waves. Intermediate particles are associated with a mixture of these two wave types. Often the waves associated with the diffuse beams steepen as if they were minishocks. The leading edge (trailing edge in the spacecraft frame) frequently appears to break up into a whistler mode wave packet. These discrete wave packets are right-hand polarized and have frequencies from below the proton gyrofrequency to well above it in the plasma frame and are blown back towards the earth by the solar wind.

463 citations


Journal ArticleDOI
TL;DR: The time asymptotic structure of a shock significantly modified by the back-reaction from the diffusive acceleration of cosmic rays is investigated in this article, and it is shown that for given upstream conditions and shock speed only a finite odd number of shock structures are possible; an explicit method of determining these is given (in many cases the solution is unique).
Abstract: The time asymptotic structure of a shock significantly modified by the back-reaction from the diffusive acceleration of cosmic rays is investigated Making a physically plausible assumption about the diffusion, it is shown that for given upstream conditions and shock speed only a finite odd number of shock structures are possible; an explicit method of determining these is given (in many cases the solution is unique) The results of this nonlinear study are contrasted with those of the linear test-particle theory and shown to confirm the possibility of efficient particle acceleration in shocks

373 citations


Journal ArticleDOI
TL;DR: In this paper, a three-parameter method for modeling the position and shape of planetary bow waves was chosen to model the near portion of the Venus, earth and Mars bow shocks, and its results were compared with those of models using one to six free variables.
Abstract: A three-parameter method for modeling the position and shape of planetary bow waves was chosen to model the near portion of the Venus, earth and Mars bow shocks, and its results were compared with those of models using one to six free variables. It was found that the relative effective shapes of the near Martian, Cytherean, and terrestrial bow shocks are ellipsoidal, paraboloidal, and hyperboloidal, respectively, in response to the increasing bluntness of the obstacles that the planets present to the solar wind. No significant deviations from axial symmetry were found when the near bow waves of the earth and Venus were mapped into the aberrated terminator plane, in agreement with gas dynamic theory predictions neglecting the effects of the IMF because of their minuteness.

342 citations


Journal ArticleDOI
TL;DR: In this article, a model of the anomalous component of the quiet-time cosmic ray flux is presented in which ex-interstellar neutral particles are accelerated continuously in the polar regions of the solar-wind termination shock, and then drift into the equatorial region of the inner heliosphere.
Abstract: A model of the anomalous component of the quiet-time cosmic ray flux is presented in which ex-interstellar neutral particles are accelerated continuously in the polar regions of the solar-wind termination shock, and then drift into the equatorial regions of the inner heliosphere. The observed solar-cycle variations, radial gradient, and apparent latitude gradient of the anomalous component are a natural consequence of this model.

300 citations


Journal ArticleDOI
TL;DR: In this paper, the distinction between two types of upstream ion populations is made on the basis of pronounced differences in their distribution functions, and the authors distinguish between reflected and diffuse ion populations.
Abstract: The distinction between two types of upstream ion populations is made on the basis of pronounced differences in their distribution functions. The reflected ions represent a fast beam with temperatures typically one-million to five-million K and speeds up to five times the solar wind speed. An important feature of the reflected ion distributions is their strong temperature anisotropy, with perpendicular temperature exceeding parallel temperature by a factor of two or three. In contrast, the diffuse ions occupy a much larger region of phase space, both in energy and angle; their distribution function generally has the form of a circular ridge in two dimensions and a spherical shell in three dimensions. Accordingly, their temperature is much larger (not less than about 10-million K) and their bulk speed is typically smaller than the solar wind speed.

249 citations


Journal ArticleDOI
TL;DR: In this paper, a high Mach number shock with parameters typical of the earth's bow shock was simulated using a hybrid (particle ions, fluid electrons) code and the simulations reproduce the observed ion reflection and overshoots in the magnetic field and density.
Abstract: Simulations of a high Mach number shock with parameters typical of the earth's bow shock have been performed using a hybrid (particle ions, fluid electrons) code. The simulations reproduce the observed ion reflection and overshoots in the magnetic field and density. These features are shown to be closely associated with ion gyration.

215 citations


Journal ArticleDOI
TL;DR: In this article, three dominant types of plasma waves are observed which are associated with energetic particle streams coming from the bow shock: ion acoustic waves, electron plasma oscillations, and whistler mode waves.
Abstract: Plasma wave and plasma data from ISEE 1 and 2 are examined. In the upstream solar wind, three dominant types of plasma waves are observed which are associated with energetic particle streams coming from the bow shock: ion acoustic waves, electron plasma oscillations, and whistler mode waves. The ion acoustic waves occur simultaneously with either ion beams or a dispersed ion population in the energy range from 0.5 to greater than 45 keV. The electron plasma oscillations are long-wavelength, nearly monochromatic electrostatic waves which are closely correlated with the flux of low-energy electrons, especially in the 0.2-1.5 keV range. Electromagnetic waves with frequencies below 200 Hz are observed when either ion beams or dispersed ion distributions are present; for these waves the refractive index determined from the wave B to E ratio is consistent with whistler mode radiation.

197 citations


Book ChapterDOI
01 Jan 1981
TL;DR: In this article, a high-energy, pulsed laser beam combined with suitable transparent overlays occn generate pressure pulses of up to 6 to 10 GPa on the surface of a metal.
Abstract: A high-energy, pulsed laser beam combined with suitable transparent overlays occn generate pressure pulses of up to 6 to 10 GPa on the surface of a metal. The propogation of these pressure pulses into the metal in the form of a shock wave produces changes in the materials micro structure and properties similar to those produced by shock waves caused in other ways. This paper reviews the mechanism of shock wave formation, calculations for predicting the pressure pulse shape and amplitude, in-depth microstructural changes and the property changes observed in metals. These property changes include increases in hardness, tensile strength and fatigue life. The increases in fatigue life appear to result from significant residual surface stresses introduced by the shock process.

157 citations


01 Apr 1981
TL;DR: In this article, the subject matter addressed by the chapters which compose this book is organized into nine sections followed by a number of appendices, and the last two chapters treat the major applications: Dynamic Compaction of Powders (8) and Explosive Metal Working and Welding (9).
Abstract: : The subject matter addressed by the chapters which compose this book is organized into nine sections followed by a number of appendices. Section 1 consists of a Historical Perspective followed by sections on High Strain-Rate Deformation, Dynamic Fracture, and Adiabatic Shearing (2,3,4). The next three sections deal with shock waves and constitute the core of the book: Shock Waves I: Experimental Techniques, Shock Waves II: Fundamentals, and Shock Waves III: Microstructural and Mechanical Effects, (5,6,7). The last two chapters treat the major applications: Dynamic Compaction of Powders (8) and Explosive Metal Working and Welding (9).

153 citations


Journal ArticleDOI
TL;DR: In this article, the characteristics of 33 diffuse particle events in the energy range from ∼30 to ∼130 keV/Q observed upstream of the earth's bow shock have been determined.
Abstract: The characteristics of 33 diffuse particle events in the energy range from ∼30 to ∼130 keV/Q observed upstream of the earth's bow shock have been determined. The measurements were made with the Ultra Low Energy Charge Analyzer (ULECA) sensor of the Max-Planck-Institut/University of Maryland instrument on ISEE-1. The energy spectra of these events are clearly steeper than power law and are generally well described by either an exponential or Maxwellian in energy per charge, with average e folding values of ∼20 keV/Q and ∼15 keV/Q, respectively. The composition in these events is remarkably constant as a function of energy per charge and is similar (within a factor of ∼2) to that of the solar wind. The particle flux is found to decay exponentially with distance from the bow shock, with an e folding distance of ∼7 RE for H and He at 30 keV/Q. Inverse velocity dispersion was observed in each event, with an average delay time of ∼40 min between the 30 keV and 130 keV proton equilibrium intensity levels. Our measurements are consistent with a Fermi acceleration mechanism and the presence of a free escape boundary upstream of the bow shock. Although existing Fermi-escape boundary models differ somewhat in detail, our present analysis is unable to differentiate among them.

Journal ArticleDOI
TL;DR: In this article, the authors examined the data from five electrostatic shocks and found that the potential associated with the shocks closed below the satellite to give rise to the parallel electric field required for the acceleration of the ion beam, and that the electrostatic ion cyclotron waves are adjacent to the shock and to extend throughout the upward-going ion beam region.
Abstract: It is noted that small-scale regions of large electric fields have been observed above the auroral zone by the S3-3 satellite. The data from five such electrostatic shocks are examined in great detail. The three higher altitude shocks (all above 5,700 km) are found to be associated with upward-going ion beams, indicating that the potential associated with the shock closed below the satellite to give rise to the parallel electric field required for the acceleration of the ion beam. In all these cases, electrostatic ion cyclotron waves are found to be adjacent to the shock and to extend throughout the upward-going ion beam region. The lack of noticeable Doppler shift in the electrostatic ion cyclotron waves in association with large convective drift velocities is seen as indicating that the wavelength of the electrostatic ion cyclotron wave can be several kilometers and that the potential difference within the wave can be on the order of 100 V.

Journal ArticleDOI
TL;DR: In this article, an instability analysis for parallel and antiparallel propagating electromagnetic waves generated by reflected and diffuse suprathermal ions upstream of the earth's bow shock is presented.
Abstract: An instability analysis is presented for parallel and antiparallel propagating electromagnetic waves generated by reflected and diffuse suprathermal ions upstream of the earth's bow shock. Calculations are performed on the basis of upstream particle observations made by the ISEE 1 Quadrispheric Lepedea instrument and low-energy electron measurements made by the ISEE 1 electron spectrometer for a single period. The electromagnetic dispersion relation is computed and the unstable modes and growth times of the fastest growing waves are determined. It is found that the reflected ions destabilize the plasma most strongly at a wave frequency 0.1 that of the ion gyrofrequency by a resonant ion beam instability for waves propagating upstream and by a nonresonant firehose-like instability for waves propagating downstream. The diffuse ions also destabilize the plasma most strongly at the same frequency by means of resonant instabilities of both right- and left-hand polarized waves propagating away from the bow shock.

Journal ArticleDOI
TL;DR: In this paper, an extended statistical analysis of the basic moments of the ions backstreaming from the earth's bow shock has been performed based on 3253 ion spectra, corresponding to a total observation time of ≃87 hours.
Abstract: Plasma data supplied by the ISEE 2 solar wind experiment are used to perform the first extended statistical analysis of the basic moments of the ions backstreaming from the earth's bow shock. The analysis is based on 3253 ion spectra, corresponding to a total observation time of ≃87 hours. It turns out that the density and total energy density of the backstreaming ions are, on the average, equal to ≃1% and ≃10% of those of the solar wind, respectively. The distinction between the ‘reflected’ and ‘diffuse’ populations has been confirmed and put on a quantitative basis using the ratio A =VBP/WBP between the bulk velocity and the rms thermal speed of the ions. The reflected ions are characterized by a bulk velocity VBP of the order of 2 times the solar wind velocity and by a temperature of ∼7 × 106 K. In contrast, the diffuse ions have, on the average, a bulk velocity 1.2 times the solar wind velocity and a temperature of 40 × 106 K. Therefore the total energy density of the diffuse ions is ≃30% larger than that of the reflected ions. Finally, the kinetic and thermal energy densities are distributed quite differently in the two ion populations: in fact, ≃70% of the total energy density is kinetic for the reflected ions, while this percentage decreases to ≃20% for the diffuse ions.


Journal ArticleDOI
TL;DR: In this paper, a physically self-consistent model for nonthermal radiation from supernova remnants in the adiabatic blast-wave (Sedov) phase of evolution, assuming relativistic electrons are accelerated in the shock to an energy density proportional to the postshock pressure, and the magnetic field is either compressed ambient field or turbulently amplified.
Abstract: We develop a physically self-consistent model for nonthermal radiation from supernova remnants in the adiabatic blast-wave (Sedov) phase of evolution, assuming relativistic electrons are accelerated in the shock to an energy density proportional to the postshock pressure, and that the magnetic field is either compressed ambient field or turbulently amplified. We have compared the resulting synchrotron profiles with observations of Tycho's remnant and find the amplified magnetic field model gives an adequate fit if there is a small radially ordered component of the magnetic field at the shock wave. The model predicts that surface brightness of Tycho declines as (diameter)/sup -4.4/ and that the flux declines by 0.25% per year. We explain the featureless power-law X-ray spectrum of the SN 1006 remnant as the extension of the radio emission: the entire spectrum can be fitted when synchrotron losses are included. The model implies that while several percent of the shock energy goes into The magnetic field, only 2 x 10/sup -5/ of the shock energy goes into relativistic electrons.

Book
01 Jan 1981
TL;DR: In this article, shock waves in chemistry, shock wave in chemistry, کتابخانه دیجیتالی دانشگاه علوم پزش-کی و خدمات درمان شهید Â
Abstract: Shock waves in chemistry , Shock waves in chemistry , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

Journal ArticleDOI
01 Dec 1981-Nature
TL;DR: In this article, the authors present a steady flow model for the blast dynamics and propose that through much of the devastated area the blast was a supersonic flow of a complex multiphase (solid, liquid, vapour) mixture.
Abstract: At 8.32 a.m. on 18 May 1980, failure of the upper part of the north slope of Mount St Helens triggered a lateral eruption (‘the blast’) that devastated the conifer forests in a sector covering ∼500 km2 north of the volcano. I present here a steady flow model for the blast dynamics and propose that through much of the devastated area the blast was a supersonic flow of a complex multiphase (solid, liquid, vapour) mixture. The shape of the blast zone; pressure, temperature, velocity (Mach number) and density distributions within the flow; positions of weak and strong internal shocks; and mass flux, energy flux, and total energy are calculated. The shape of blast zone was determined by the initial areal expansion from the reservoir, by internal expansion and compression waves (including shocks), and by the density of the expanding mixture. The pressure within the flow dropped rapidly away from the source of the blast until, at a distance of ∼11 km, the flow became underpressured relative to the surrounding atmosphere. Weak shocks within the flow subparallel to the east and west margins coalesced at about this distance into a strong Mach disk shock, across which the flow velocities would have dropped from supersonic to subsonic as the pressure rose back towards ambient. The positions of the shocks may be reflected in differences in the patterns of felled trees. At the limits of the devastated area, the temperature had dropped only 20% from the reservoir temperature because the entrained solids thermally buffered the flow (the dynamic and thermodynamic effects of the admixture of the surrounding atmosphere and the uprooted forest and soils into the flow are not considered). The density of the flow decreased with distance until, at the limits of the blast zone, 20–25 km from the volcano, the density became comparable with that of the surrounding (dirty) atmosphere and the flow became buoyant and ramped up into the atmosphere. According to the model, the mass flux per unit area at the source was 0.6 × 104 g s−1 cm−2 and the energy flux per unit area was 2.5 MW cm−2. From the measured total ejected mass, 0.25 × 1015 g, the total energy released during the eruption was 1024 erg or 24 megatons. The model, triggering of the eruption and the transition from unsteady to steady flow, and applications to eyewitness observations and atmospheric effects are discussed in ref. 1.

Journal ArticleDOI
TL;DR: In this paper, a strong bi-directional streaming of solar wind electrons greater than about 80 eV was observed with Los Alamos instrumentation on ISEE 3 for many hours simultaneously parallel and anti-parallel to the interplanetary magnetic field which was directed roughly perpendicular to the sun-satellite line.
Abstract: In near time coincidence with the arrival of helium enriched plasma driving the shock wave disturbance of November 12-13, 1978, strong bi-directional streaming of solar wind electrons greater than about 80 eV was observed with Los Alamos instrumentation on ISEE 3. The streaming persisted for many hours simultaneously parallel and anti-parallel to the interplanetary magnetic field which was directed roughly perpendicular to the sun-satellite line. This example of bidirectional streaming cannot be explained by field line connection to the earth's bow shock or the outward propagating interplanetary shock which passed ISEE 3 approximately 16 hours earlier. The event is explained if the local interplanetary field was a part of a magnetic bottle rooted at the sun or a disconnected loop propagating outward.

Journal ArticleDOI
TL;DR: In this paper, strong asymmetries in the ion angular pitch angle distribution are often observed, a consequence of the sharp gradient in guiding center density and very weak scattering, due to the restricted spatial region over which these particles are accelerated.
Abstract: Electrons and ions moving upstream frequently appear at distances up to 240 earth radii from earth at times when the direction of the interplanetary magnetic field allows their propagation from the bow shock. Strong asymmetries in the ion angular pitch angle distribution are often observed, a consequence of the sharp gradient in guiding center density and very weak scattering. The gradient is due to the restricted spatial region over which these particles are accelerated. The solar wind electric field acts on these particles and produces striking effects in both the ion angular distributions and the ion energy spectra. The frequent occurrence of these effects implies that the source region of the diffuse ions at the bow shock is not more than a few tens of thousands of km.

Journal ArticleDOI
TL;DR: In this paper, an isotropic flowing Maxwellian distribution was used to model the count rate modulations of the observed upstream ion population, and the authors obtained estimates of the local plasma temperature and three-dimensional flow velocity.
Abstract: The unexpected appearance of spin modulations in the fixed voltage electrostatic analyzer detectors on ISEE 1 and 2 has made it possible to study the plasma properties of the upstream ions in high time resolution. Using an isotropic flowing Maxwellian distribution to model the count rate modulations, estimates have been obtained of the local plasma temperature and three-dimensional flow velocity of the observed upstream ion population. It is found that in almost all of the observations of upstream particles there exist beam-like ions with temperatures in the range 5-80 eV. Their flow velocities cannot be ordered by E x B. This last point separates these observations from the previously reported reflected and diffuse populations of upstream ions. Mechanisms that can gyrophase bunch the ions reflected at the bow shock are discussed as a method of explaining the data.



Journal ArticleDOI
TL;DR: In this paper, a model of particle acceleration in a finite two-dimensional shock perpendicular to the magnetic field is presented, with particle parallel and perpendicular diffusion coefficients inversely proportional to each other.
Abstract: Particle acceleration and escape at the earth's bow shock wave are discussed in order to account for reported exponential fast particle spectra. A model is presented of particle acceleration in a finite two-dimensional shock perpendicular to the magnetic field, with particle parallel and perpendicular diffusion coefficients inversely proportional to each other. It is shown that the exponential particle energy per unit charge spectra observed by Ipavich et al. (1979) for the case of a radial solar wind magnetic field may be obtained if the fast particles escape the shock by means of resonant diffusion to unconnected field lines. The calculated e-folding value of the energy/charge ratio is found to be independent of the level of turbulence near the shock and in good agreement with observations. For the case of a nonradial solar wind magnetic field, the model is noted to predict that convection may be the dominant means of escape. It is also pointed out that the parallel and perpendicular diffusion coefficients may be measured indirectly at the bow shock.


Journal ArticleDOI
TL;DR: In this article, a further development of the Kostyuk-Pikelner's model is presented, where the response of the chromosphere heated by non-thermal electrons of the power-law energy spectrum has been studied on the basis of the numerical solution of the one-dimensional time-dependent equations of gravitational gas dynamics.
Abstract: A further development of the Kostyuk-Pikelner's model is presented. The response of the chromosphere heated by non-thermal electrons of the power-law energy spectrum has been studied on the basis of the numerical solution of the one-dimensional time-dependent equations of gravitational gas dynamics. The ionization and energy loss for the emissions in the Lyman and Balmer lines have been determined separately for the optically thin and thick Lα-line layers. Due to the initial heating, a higher-pressure region is formed. From this region, disturbances propagate upwards (a shock wave with a velocity of more than 1000 km s-1) and downwards. A temperature jump propagates downwards, and a shock is formed in front of the thermal wave. During a period of several seconds after the beginning of this process, the temperature jump intensifies the downward shock wave and the large radiative loss gives rise to the high density jump (ϱ2/ϱ1 ∼ 100). The numerical solution has been analyzed in detail for the case heating of the ionized and neutral plasma, and a value of this heating is close to the upper limit of the admissible values. In this case, the condensation located between the temperature jump and the shock wave front, may emit in the observed optical continuum.


Journal ArticleDOI
TL;DR: In this article, the authors compared the energy spectra of the upstream energetic ions (up to approx.150 keV per charge) with the expectations from a first-order Fermi acceleration process, i.e., a multiple reflection process between the bow shock and the upstream wave field.
Abstract: The observed energy spectra of the upstream energetic ions (up to approx.150 keV per charge) are compared with the expectations from a first-order Fermi acceleration process, i.e., a multiple reflection process between the bow shock and the upstream wave field. The escape of particles into the far upstream region (> or approx. = several tens to 100 R/sub E/) is found important for the formation of the energy spectrum. The predicted energy spectrum has exponential dependence on energy like N(E)dEapprox.exp (-E/E/sub c/)dE, which is consistent with the observation. One of the remarkable features of the observation, the invariance of the abundance ratios among various ion species when evaluated at the same energy per charge, can also be explained by the Fermi acceleration process: At the same energy per charge, the elementary acceleration process at the shock front is more efficient for particles of higher mass to charge ratio (M/Q), while the scattering process in the upstream waves is less efficient for these particles. It is shown that the above two effects compensate each other and make the energy spectra of accelerated particles independent of particle species when evaluated by energy per charge unit.

Journal ArticleDOI
TL;DR: In this article, a brief review of short wavelength fluctuations and their associated phenomena upstream of the earth's bow shock is presented, where sources of free energy, the most unlikely instabilities, and the associated nonlinear consequences that may be observed are discussed.
Abstract: This is a brief review of short wavelength fluctuations and their associated phenomena upstream of the earth's bow shock. Sources of free energy, the most unlikely instabilities, and the associated nonlinear consequences that may be observed are discussed.

Journal ArticleDOI
TL;DR: In this paper, a simple model of the earth's bow shock is presented and compared with ISEE-1 observations of diffuse ions upstream of the shock, showing that the diffusion coefficient must increase faster than linearly with velocity, and providing an upper limit to the acceleration efficiency defined as the proportion of incoming solar wind ions accelerated and observed upstream.
Abstract: A simple model of the earth's bow shock is presented and compared with ISEE-1 observations of diffuse ions upstream of the shock. Ion behavior is modeled in a test particle simulation using Monte Carlo techniques for a plane parallel shock at which cold solar wind ions are heated sufficiently to allow diffusion back upstream. Fitting of the model to the observations indicates that the diffusion coefficient must increase faster than linearly with velocity, and provides an upper limit to the acceleration efficiency defined as the proportion of incoming solar wind ions accelerated and observed upstream. Results suggest that astrophysical shocks are capable of accelerating ions directly from the thermal plasma without the need for a distinct preenergizing injection stage.