A model of generation of a jet in stratified nonequilibrium plasma

TL;DR

This paper develops an analytical magnetohydrodynamic model describing the initial formation and dynamics of jets in stratified nonequilibrium plasma, highlighting instability mechanisms and velocity field evolution.

Contribution

It introduces a new nonlinear analytical model for jet formation in stratified plasma, incorporating magnetic and velocity field dynamics based on Schwarzschild's instability.

Findings

Jets with poloidal velocity fields are generated in stratified plasma.

Velocity components grow over time following a hyperbolic sine law.

The model describes the structure and nonlinear dynamics of jets in detail.

Abstract

In the magnetohydrodynamic approximation, system of equations is proposed which analytically describes the initial stage of origination of axially symmetric directed flows in nonequilibrium stratified plasma. The mechanism of generation is based on the Schwarzschild's convective instability and uses the frozen-in flux condition for magnetic field lines. A solution to the nonlinear equation for the stream function is obtained and analyzed, and it is shown that jets with poloidal velocity fields are generated in such a plasma. The corresponding expressions for the R-dependences of the radial and vertical velocity components in the internal and external regions of the jet include Bessel functions and modified Bessel functions. For jets localized in height and radius, the proposed new nonlinear analytical model makes it possible to study their structure and nonlinear dynamics in the radial and vertical directions. The emerging instability in a stratified plasma leads to an increase in the radial and vertical velocities of flows according to the law of the hyperbolic sine. The characteristic growth time depends on the value of the imaginary part of the Brunt-Vyaisyalya frequency. The formation of jets with finite velocity components increasing with time is analyzed. The radial structure of the azimuthal components is determined by the structure of the initial perturbation and can vary with altitude. Along with studying the dynamics of the velocity field, the change in the vertical magnetic field, as well as the dynamics and structure of the emerging toroidal electric current, are investigated.