Numerical Study on Acceleration and Deceleration Mechanism of Weakly Ionized Plasma Flowing Supersonically Through Open Field Line

Abstract

We study supersonic flow of rarefied weakly ionized plasma at diverging magnetic field. While the flows of ions and neutral are treated by particle-based direct simulation Monte Carlo method, the electron is treated as a fluid, i.e., we carried out hybrid simulation. We calculate number density, velocity, temperature, and electric potential of charged particles and neutrals when the arc plasma flows out of the uniform magnetic field into lower pressure region in a steady state. We find the velocity increase just after passing the open magnetic field line, followed by deceleration due to collisions with residual molecules. We also find the temperature increase during the deceleration. In this acceleration/deceleration phenomena, the velocity difference between the neutrals and charged species are found, which also changes the electric potential. We discuss the mechanisms of potential formation along the plasma flow mainly by the pressure difference and the friction force between the charged particles and neutral species. The numerical results are, at least qualitatively, consistent with our previous experimental results.Index Terms-Diverging magnetic field, hybrid simulation, ion slip, potential drop, rarefied flow, supersonic plasma flow, weakly ionized plasma.

Numerical study of electric potential formation in a weakly ionized plasma flowing supersonically through open magnetic field lines

“…Figure 1 shows the numerical result for the dependence of the space potential drop on the background pressure calculated by the method described in Ref. 20. The result indicates that the lower the background pressure, the greater the space potential drop.…”

“…15) We also carried out a simulation to clarify the acceleration and deceleration mechanisms of a plasma flowing supersonically through open field lines. 20) Ions and neutrals were treated by the particle-based direct simulation Monte Carlo (DSMC) method, while electrons were treated as a fluid. In the simulation, we assumed the following three conditions.…”

“…To understand the present plasma flow with a low ionization degree, however, the effect of the space potential drop on the electron velocity should also be determined, because the electric field may contribute to the acceleration of ions, whereas electrons are decelerated, especially when the background pressure is low. (Color online) Variation in the background pressure of the space potential ϕ on the z-axis when r = 0, for 0.0, 0.3, 0.5, and 0.7 times the neutral density of 2.4 × 10 20 m −3 , when the temperature is fixed at 300 K. 20) To overcome this problem, we add an electron continuity equation to calculate the electron velocity as a fluid independent of the ions, while the ions are treated by the DSMC method similarly to that in our previous modeling. 20) In this paper, we first review our experiments and results, which is followed by an explanation of the information required for numerical modeling.…”

“…(Color online) Variation in the background pressure of the space potential ϕ on the z-axis when r = 0, for 0.0, 0.3, 0.5, and 0.7 times the neutral density of 2.4 × 10 20 m −3 , when the temperature is fixed at 300 K. 20) To overcome this problem, we add an electron continuity equation to calculate the electron velocity as a fluid independent of the ions, while the ions are treated by the DSMC method similarly to that in our previous modeling. 20) In this paper, we first review our experiments and results, which is followed by an explanation of the information required for numerical modeling. Finally, we compare the numerical results with the results of our previous experiments.…”

Numerical Simulation of the Chemical Combination and Dissociation Reactions of Neutral Particles in a Rarefied Plasma Arc Jet

“…Recently, Tsuno et al [14] have studied supersonic rarefied weakly ionized plasma flows for the expanding arc jet in a diverging magnetic field, and the ions and the neutrals were treated by the particle scheme in the DSMC method, while the electrons are treated by the fluid scheme with a self-consistent electric field. Korkut et al [2] have developed an adaptive mesh refinement combined with the Octree method for the…”