Generalized Cross Helicity in Non-ideal Magnetohydrodynamics

TL;DR

This paper investigates how dissipative processes like thermal conduction, electrical conductivity, and viscosity affect the conservation of generalized cross helicity in non-ideal magnetohydrodynamics, revealing conditions under which it remains conserved.

Contribution

It extends the understanding of cross helicity conservation from ideal to non-ideal MHD by analyzing the effects of dissipation on its constancy.

Findings

Generalized cross helicity is not conserved in non-ideal MHD due to dissipation.

Certain configurations preserve cross helicity despite dissipative effects.

Analytical expressions for the time derivative of cross helicity are derived.

Abstract

The objective of the present paper is to investigate the constancy of the topological invariant denoted non-barotropic generalized cross helicity in the case of non-ideal magnetohydrodynamic (MHD). Existing work considers only ideal barotropic MHD and ideal non-barotropic MHD. The non-ideal MHD case was not explored probably because of its mathematical complexity. Here we consider dissipative processes in the form of thermal conduction, finite electrical conductivity and viscosity and the effect of these processes on the cross helicity conservation. Analytical approach has been adopted to obtain the mathematical expressions for the time derivative of cross helicity. Obtained results show, that the generalized cross helicity is not conserved in the non-ideal MHD limit and indicate which processes affect the helicity and which do not. Furthermore, we indicate the configurations in which this topological constant is conserved despite the dissipative processes.