Magnetic nozzle and plasma detachment model for a steady-state flow

Abstract

Plasma propulsion concepts that employ a guiding magnetic field raise the question of how the magnetically controlled plasma can detach from the spacecraft. This paper presents a detachment scenario relevant to high-power thrusters in which the plasma can stretch the magnetic field lines to infinity, similar to the solar wind. In previous work, the corresponding ideal magnetohydrodynamics equations have been solved analytically for a plasma flow in a slowly diverging nozzle. That solution indicates that efficient detachment is feasible if the nozzle is sufficiently long. In order to extend the previous model beyond the idealizations of analytical theory, a Lagrangian code is developed in this work to simulate steady-state kinetic plasma flows and to evaluate nozzle efficiency. The code is benchmarked against the analytical results and then used to examine situations that are not analytically tractable, including plasma behavior in the recent Detachment Demonstration Experiment at the National Aeronautics and Space Administration.

Trapped particle stability for the kinetic stabilizer

“…When β becomes larger than unity, typically the field-lines cannot collimate the plasma because selfconsistent effects drive the plasma across field-lines [12]. For the injected kinetic stabilizer ions, the local β ks = 2µ 0 p/B 2 must be less than unity along the imposed field-lines.…”

Numerical Investigation of Near-Field Plasma Flows in Magnetic Nozzles

“…Other investigations, such as that found in Ref. [1], discuss the far-field region. Nevertheless, observations of plasma behavior in the near-field of the magnetic nozzle have proved to be informative and the results from this simulation can be extrapolated to estimate far-field behavior and can yield self-consistent boundary conditions for far-field simulations.…”

“…However, due to the solenoidal nature of the magnetic field it is essential to ensure that the plasma detaches from the field, making this a problem of active research. 1,2 While other investigations have looked into far-field phenomena, like detachment, this paper discusses numerical simulations of the near-field behavior of plasma jets in magnetic nozzles, where the applied field gradients are greatest. The development of a multidimensional numerical tool that can be used to investigate plasma detachment mechanisms was introduced in Ref.…”

Magnetic Detachment and Plume Control in Escaping Magnetized Plasma

“…Arefiev and Breizman describe magnetized ideal MHD flow constrained to be field-directed everywhere and characterize successful detachment by the transition of plasma flow from a sub-Alfvénic to a super-Alfvénic regime [1,2]. Physically, the detached plume is said to stretch the frozen-in magnetic field lines to infinity.…”

“…Several models have been proposed to describe the physics of magnetic plasma detachment [1][2][3][4]. Arefiev and Breizman describe magnetized ideal MHD flow constrained to be field-directed everywhere and characterize successful detachment by the transition of plasma flow from a sub-Alfvénic to a super-Alfvénic regime [1,2].…”