Basic scalings for collisionless-shock experiments in a plasma without pre-imposed magnetic field

Abstract

In this paper, scaling relations pertinent to collisionless-shock experiments are derived. Two oppositely directed, non-relativistic interpenetrating plasma streams are considered. A full set of collisionless Vlasov-Maxwell equations is used to describe the plasma streams. Two scaling parameters are identified for those streams in which the initial temperature is small compared with the final temperature. If the scaling parameters are held constant between the two systems, the knowledge of the behavior of one of the systems allows for a direct prediction of behavior of the other, irrespective of differences in, for example, the plasma density. This similarity covers both hydrogen and non-hydrogen ion species. Reduced versions suitable for assessing electrostatically mediated and magnetically mediated (Weibel-like) models of the shocks are described. In these limiting cases, the number of scaling parameters reduces to one, making the similarity quite broad. The presence of these scaling relations can serve as a basis for making comparisons between models and selecting the most plausible models. A brief discussion is presented of the constraints associated with the role of intra-jet collisions, whose frequency may be non-negligible even if the collisions between the particles of two jets are very rare.

Visualizing electromagnetic fields in laser-produced counter-streaming plasma experiments for collisionless shock laboratory astrophysics

“…33 and 59) scales in a way that is inversely proportional to the square root of particle density n. This conclusion is supported by a model-independent scaling analysis. 16 In order to satisfy the left-hand inequality in Eq. (11), one is, therefore, pushed in the direction of higher density, in order to shrink the micro-physics into the laboratory system.…”

“…Laboratory experiments are a powerful tool to explore these questions in a scaled-down setting under controlled conditions. 15,16 Since many collisionless shocks are a) Paper KI3 3, Bull. Am.…”

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“…Recent developments in pulsed-power technology have increased the possibilities for creating laboratory experiments relevant to astrophysical processes. Scaling arguments [6][7][8][9][10] allow us to make reasonable comparisons between lab-scale and astro-scale plasmas if they are sufficiently similar. Extending the parameter space which laboratory experiments can access increases the likelihood that we can produce results of wide interest.…”

Radiation-pressure-driven ion Weibel instability and collisionless shocks

“…Today's high-intensity laser facilities open new possibilities for the study, in the laboratory, of scenarios relevant to various astrophysical processes, among which collisionless shocks have recently attracted remarkable interest [1][2][3][4][5][6][7][8]. Collisionless shocks are ubiquitous in a wide range of astrophysical environments (active galaxy nuclei, pulsar wind nebulae, supernovae remnants, etc.).…”