Propagation dynamics of successive emissions in laboratory and astrophysical jets and problem of their collimation

Abstract

This paper presents the results of numerical simulation of the propagation of a sequence of plasma knots in laboratory conditions and in the astrophysical environment. The physical and geometric parameters of the simulation have been chosen close to the parameters of the PF-3 facility (Kurchatov Institute) and the jet of the star RW Aur. We found that the low-density region formed after the first knot propagation plays an important role in the collimation of the subsequent ones. Assuming only the thermal expansion of the subsequent emissions, qualitative estimates of the time taken to fill this area with the surrounding matter and the angle of jet scattering have been made. These estimates are consistent with observations and results of our modeling.

The Collimated Propagation Causes of Astrophysical and Laboratory Jets

“…In addition, laboratory and astrophysical plasma energy loss due to radiation according to different laws. For parameters close to those observed for object HH 229, we have already performed numerical modeling of successive ejections [12], and the effect associated with the vacuum trace was confirmed. To find out to what extent the effect discovered in the laboratory is applicable to astrophysics, a numerical simulation was performed with the resulting scaling parameters.…”

“…The simulation results carried out in our previous paper [12] predicted the vacuum trace formation fol- lowing the passage of the first ejection and its critical influence on the collimation of subsequent ones if the working gas in the laboratory facility is argon. Subsequent experiments with helium as the working gas confirmed this effect, which is presented in Subsection 2.2.…”

“…Knowing the behavior of system "1", the behavior of system "2" can be restored using the specified scaling. For example, the density value of the system "2" is expressed through the density value of the system "1" as follows: (12) With the results of modeling laboratory emissions, it is enough to apply the scaling laws described above and obtain a description for the dynamics of the astrophysical jet propagation. However, these laws do not consider the possibly different radiative characteristics of both systems.…”

“…Thus, both laboratory experiments described in Subsection 2.2 and the results of numerical simulations for hydrogen, argon, presented in our previous paper [12], and for helium, contained in this section. According to the scaling laws (9)-( 12) and the results of modeling the single jet propagation with and without radiation cooling, a similar behavior would be expected from ejections whose parameters are close to astrophysical ones.…”

“…In our previous paper [12], using numerical simulations, we showed that both in astrophysical and laboratory conditions, after the passage of a supersonic plasma ejection through the environment, a region with low density remains behind it, the so-called vacuum trace. Due to this, subsequent ejections experience much less resistance from the ambient and spread in a more collimated manner-almost all the matter of such an ejection remains within its original radial boundaries.…”