Newtonian nonlinear hydrodynamics and magnetohydrodynamics

TL;DR

This paper develops a covariant formalism to analyze the nonlinear evolution of self-gravitating, magnetized fluids in Newtonian physics, aiming to better understand complex astrophysical plasma systems.

Contribution

It introduces a covariant approach to nonlinear Newtonian hydrodynamics and magnetohydrodynamics, extending previous relativistic methods for clearer analysis of magnetic effects.

Findings

Derived nonlinear electrodynamic equations for resistive and conductive fluids.

Applied covariant formalism to magnetized media, isolating magnetic effects on kinematics.

Facilitated comparison with relativistic studies to identify key differences.

Abstract

We use covariant methods to analyse the nonlinear evolution of self-gravitating, non-relativistic media. The formalism is first applied to imperfect fluids, aiming at the kinematic effects of viscosity, before extended to inhomogeneous magnetised environments. The nonlinear electrodynamic formulae are derived and successively applied to electrically resistive and to highly conductive fluids. By nature, the covariant equations isolate the magnetic effects on the kinematics and the dynamics of the medium, combining mathematical transparency and physical clarity. Employing the Newtonian analogue of the relativistic 1+3 covariant treatment, also facilitates the direct comparison with the earlier relativistic studies and helps to identify the differences in an unambiguous way. The purpose of this work is to set the framework and take a first step towards the detailed analytical study of complex nonlinear systems, like non-relativistic astrophysical plasmas and collapsing protogalactic clouds.