“Alfvenization” of plasma flow in the magnetic mirror: Plasma rotation and electromagnetic effects.

Plasma flow and acceleration in the magnetic nozzle with converging-diverging magnetic configuration are important for applications in electric propulsion and fusion systems such as open mirrors and tokamak divertors. The paraxial fluid model for acceleration of cold ions by the electron pressure [1] has been extended to include the effects of warm ions with anisotropic ion pressure resulting in additional acceleration due to the ion mirror force [2]. Further generalization includes the role of the induced azimuthal magnetic field and plasma rotation. Azimuthal magnetic and azimuthal magnetic field represent the basic polarization of the circular polarized Alfven wave. Therefore, the problem reduces to the problem of Alfven waves propagating in the inhomogeneous magnetic field. It is shown that the inhomogeneous magnetic field couples the axial plasma flow with the evolution of the azimuthal magnetic field and plasma rotation resembling the problem of the thermally and magnetically driven flows in astrophysical jets and winds. It is shown that that plasma rotation provides an additional energy available for acceleration (swirl acceleration) while the energy of the azimuthal magnetic field is a source of the acceleration due to the axial current. The role of the Alfven, slow, and fast magnetosonic point singularities in plasma acceleration is discussed. The local value of the Alfven velocity decreases with the magnetic field so the the Alfvenic point can be reached for large mirror expansion ratio.

[1] A.I. Smolyakov, A. Sabo, P. Yushmanov, and S. Putvinski. "On Quasineutral Plasma Flow in the Magnetic Nozzle." Physics of Plasmas 28, 060701 (2021).

[2] A. Sabo, A. I. Smolyakov, P. Yushmanov, and S. Putvinski. "Ion Temperature Effects on Plasma Flow in the Magnetic Mirror Configuration." Physics of Plasmas 29, 052507 (2022).