Experimental Observations of Collisionless Shock Waves in a Magnetized Plasma
Author: J.W.M. Paul
Publisher:
Published: 1965
Total Pages: 10
ISBN-13:
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Author: J.W.M. Paul
Publisher:
Published: 1965
Total Pages: 10
ISBN-13:
DOWNLOAD EBOOKAuthor: André Balogh
Publisher: Springer Science & Business Media
Published: 2013-01-04
Total Pages: 503
ISBN-13: 1461460999
DOWNLOAD EBOOKThe present book provides a contemporary systematic treatment of shock waves in high-temperature collisionless plasmas as are encountered in near Earth space and in Astrophysics. It consists of two parts. Part I develops the complete theory of shocks in dilute hot plasmas under the assumption of absence of collisions among the charged particles when the interaction is mediated solely by the self-consistent electromagnetic fields. Such shocks are naturally magnetised implying that the magnetic field plays an important role in their evolution and dynamics. This part treats subcritical shocks which dissipate flow energy by generating anomalous resistance or viscosity. The main emphasis is, however, on super-critical shocks where the anomalous dissipation is insufficient to retard the upstream flow. These shocks, depending on the direction of the upstream magnetic field, are distinguished as quasi-perpendicular and quasi-parallel shocks which exhibit different behaviours, reflecting particles back upstream and generating high electromagnetic wave intensities. Particle acceleration and turbulence at such shocks become possible and important. Part II treats planetary bow shocks and the famous Heliospheric Termination shock as examples of two applications of the theory developed in part I.
Author: George Charles Goldenbaum
Publisher:
Published: 1966
Total Pages: 168
ISBN-13:
DOWNLOAD EBOOKContents: The laminar one fluid approach; The laminar two fluid approach; The piston problem; Summary of the laminar approach; Turbulence; Vacuum and gas filling systems; Trigatron spark gap switches; Production of the initial plasma and magnetic field; Generation of the shock wave; Grounding and shielding; Coil voltage measurements; Magnetic field measurements; Emission spectroscopy; Magnetic structure measurements; Electron temperature measurements.
Author: Peter Ver Bryck Heuer
Publisher:
Published: 2020
Total Pages: 164
ISBN-13:
DOWNLOAD EBOOKQuasi-parallel collisionless shocks are objects of considerable interest in space and astrophysics, most notably as possible sites of cosmic ray acceleration. Such shocks occur naturally in systems such as supernova remnants and planetary bow shocks, where the complex and turbulent structures they form are commonly observed by spacecraft. However, \textit{in situ} spacecraft measurements have some inherent limitations, such as a moving reference frame and non-repeatable measurements. Generating a quasi-parallel collisionless shock in a repeatable, well-diagnosed laboratory environment could therefore improve our understanding of their formation and structure. The quasi-parallel collisionless shocks observed in space and astrophysics are far too large to fit in a laboratory, but scaled versions of these systems can be created using smaller, denser plasmas with similar dimensionless parameters. However, quasi-parallel collisionless shocks are particularly challenging to scale to a feasible experiment. The shock formation process is mediated by several electromagnetic ion/ion beam instabilities which require long length scales ($>500$ ion-inertial lengths) to grow, so an experiment must include a long magnetized background plasma. This background plasma must be overlapped over the same length by a highly super-Alfv\'enic beam plasma. Matching the dimensionless parameters of the shocks observed in space sets demanding requirements on the densities of both plasmas as well as the background magnetic field strength. Laser-produced plasmas (LPPs) provide a promising beam plasma source (a ``driver'') for such experiments. A recent experimental campaign has been conducted at UCLA to investigate the potential of LPPs as drivers of quasi-parallel collisionless shocks. These experiments combine one of two high-energy lasers with the magnetized background plasma of the Large Plasma Device (LAPD) to drive the electromagnetic ion/ion beam instabilities responsible for shock formation. The experiments have observed electromagnetic waves consistent with the very early stages of quasi-parallel shock formation. These waves are similar to the ultra-low frequency (ULF) waves observed by spacecraft upstream of the Earth's quasi-parallel bow shock. At present, the amplitudes of the waves generated by these experiments are too low ($dB/B_0 \sim 0.01$) to fully form a quasi-parallel shock. The wave amplitudes observed in these experiments are low because the conditions for beam instability growth are only met in a small region near the laser target. Outside of this region, decreasing LPP density due to velocity dispersion and cross-field transport terminates the wave growth and consequently the shock formation process. Future experiments will require technical innovations to expand this growth region in order to produce larger-amplitude waves. Promising approaches including trains of laser pulses and heating electrons in the background plasma to reduce collisional cross-field transport. Along with comparisons to analytic theory and simulations, the results of the current experiments can inform the design of future laboratory quasi-parallel shock experiments.
Author: Derek A. Tidman
Publisher: John Wiley & Sons
Published: 1971
Total Pages: 202
ISBN-13:
DOWNLOAD EBOOKAuthor: Derek A. Tidman
Publisher: John Wiley & Sons
Published: 1971
Total Pages: 200
ISBN-13:
DOWNLOAD EBOOKAuthor: William E. Drummond
Publisher:
Published: 1969
Total Pages: 112
ISBN-13:
DOWNLOAD EBOOKThe work covered by this report is part of an experimental program to study oblique shock waves in plasma. The support from DASA under this contract was for the continuation of the experimental program with particular regard to measurements on shock using light scattering techniques. The measurements made on the Texas oblique shock experiment were first detailed investigation of the magnetic and electronic structure of the oblique shock. Compared to the fairly extensive body of information which exists on shocks moving perpendicular to the magnetic field, there had previously been only very scanty results on oblique shocks. This was largely because the oblique shock has a larger scale length (approx. c/omega sub pi) than the perpendicular shock (approx. c/omega sub pe), and consequently experiments designed from the onset to study the oblique shock, and was significantly larger in scale (50 cm diameter) than most shock experiments. The experiment has yielded unique information about the structure of oblique shocks.
Author:
Publisher:
Published: 1995
Total Pages: 10
ISBN-13:
DOWNLOAD EBOOKCollisionless shock waves are a very important heating mechanism for plasmas and are commonly found in space and astrophysical environments. Collisionless shocks were studied in the laboratory more than 20 years ago, and more recently in space via in situ satellite measurements. The authors propose a new laboratory shock wave experiment to address unresolved issues related to the differences in the partition of plasma heating between electrons and ions in space and laboratory plasmas, which can have important implications for a number of physical systems.
Author: Robert G. Stone
Publisher: American Geophysical Union
Published: 1985
Total Pages: 306
ISBN-13: 0875900615
DOWNLOAD EBOOKPublished by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 35. Violent expansions of the solar corona cause transient shock waves which propagate outward from the sun at hundreds to thousands of kilometers per second; simple solar wind velocity gradients at the surface of the sun lead to high-speed streams overtaking slower streams, forming corotating shocks; and steady state supermagnetosonic solar wind flow past objects such as the planets lead to standing bow shocks. However, the solar wind plasma is so hot and tenuous that charged particle Coulomb collisions produce negligible thermalization or dissipation on scale sizes less than 0.1 AU. The irreversible plasma heating by these shocks is accomplished by wave-particle interactions driven by plasma instabilities. Hence these shocks are described as "collisionless."
Author: Ralph H. Lovberg
Publisher:
Published: 1973
Total Pages: 31
ISBN-13:
DOWNLOAD EBOOKThe report discusses an experiment designed to study collisionless shock waves in an inverse pinch discharge using argon. A magnetic disturbance was generated which propagated ahead of the driving field at twice the piston speed. Measurements of the magnetic and electric field structures, electron density and temperature, as well as ion velocities revealed that the disturbance was produced by a beam of plasma moving through the ionized ambient plasma rather than by a true shock wave. Calculations of ion trajectories using measured electric fields demonstrated that the beam originated at small radii and early times, and was not the result of a steady specular reflection from the piston field. It is concluded that the ions comprising this stream, which were collisionless relative to the ambient ions, did not couple to the background plasma even though a strong magnetic field was applied. (Author).