Electromagnetic and Centrifugal Effects on Plasma Acceleration in the Magnetic Nozzle

TL;DR

This paper investigates plasma acceleration mechanisms in magnetic nozzles, emphasizing electromagnetic and centrifugal effects, demonstrating the existence of stable, transonic, and trans-Alfvenic flow solutions within MHD theory.

Contribution

It introduces a detailed analysis of electromagnetic and centrifugal effects on plasma acceleration, revealing stable stationary solutions in magnetic nozzles with potential applications in propulsion and fusion.

Findings

Plasma velocities can approach and exceed Alfven velocity in diverging magnetic fields.

Unique regular solutions pass through all critical MHD points, ensuring physical consistency.

Time-dependent simulations confirm the stability and robustness of stationary plasma flows.

Abstract

Plasma flow and acceleration in the converging-diverging magnetic field configuration, such as magnetic nozzle in electric propulsion and open magnetic mirrors for fusion applications are considered. This work analyses plasma acceleration in the magnetic nozzle with an emphasis on the electromagnetic effects and centrifugal forces due to plasma rotation. Intrinsic coupling of the azimuthal rotation and azimuthal magnetic field is analyzed, and additional plasma acceleration due to the conversion of the energy of the azimuthal magnetic field and azimuthal rotation is demonstrated. For large expansion in the diverging magnetic field plasma flow velocities may approach and exceed the Alfven velocity. In these regimes, stationary solutions for the transonic and trans-Alfvenic flows have been obtained that demonstrate the existence of the unique regular solution passing through all critical points within the MHD theory, i. e. the points where the plasma flow is equal to the signal velocities of the MHD modes: slow and fast magnetohydrodynamic waves and Alfven wave. The time-dependent initial value simulations show that stationary equilibrium flows are robust and stable, so that time-dependent solutions converge toward stationary solutions.