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The 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.
The 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).
An engaging introduction to collisionless shocks in space plasmas, presenting a complete review, from first principles to current research.
The 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.
Collisionless 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.
Published 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."