Partial-Ionization Deconfinement Effect in Magnetized Plasma

TL;DR

This paper investigates how partial ionization in plasma causes ions to deconfine across magnetic fields due to charge state equilibration and ion-ion friction, differing from fully ionized plasma behavior.

Contribution

It introduces a new understanding of ion deconfinement driven by charge state dynamics and multi-ion transport in partially ionized magnetized plasma.

Findings

Ion deconfinement occurs on a timescale similar to multi-ion transport.

Charge state equilibration enforces disparities in ion drift velocities.

Deconfinement is driven by ion-ion friction, not electron-ion interactions.

Abstract

In partially ionized plasma, where ions can be in different ionization states, each charge state can be described as a different fluid for the purpose of multi-ion collisional transport. In the case of two charge states, transport pushes plasma toward equilibrium which is found to be a combination of local charge state equilibrium and generalized pinch relations between ion fluids representing different charge states. Combined, these conditions lead to a dramatic deconfinement of ions. This deconfinement happens on the timescale similar but not identical to the multi-ion cross-field transport timescale, as opposed to electron-ion transport timescale in fully ionized plasma. Deconfinement occurs because local charge state equilibration enforces the disparity in diamagnetic drift velocities of ion fluid components, which in turn leads to the cross-field transport due to ion-ion friction.