Magnetic Shear Damped Polar Convective Fluid Instabilities

TL;DR

This paper investigates how magnetic shear influences convective plasma instabilities in the high latitude ionosphere, showing that magnetic shear can suppress growth rates at larger scales but not at smaller, scintillation-causing scales.

Contribution

It provides new insights into the stabilizing effects of magnetic shear on ionospheric plasma instabilities, highlighting scale-dependent behavior and mode localization.

Findings

Magnetic shear reduces growth rates of large-scale instabilities.

Small-scale instabilities (~a few km) are largely unaffected by magnetic shear.

Eigenmodes are localized near rational surfaces with broken symmetry due to flow or current.

Abstract

The influence of the magnetic field shear is studied on the $E\times B$ (and/or Gravitational) and the Current Convective Instabilities (CCI) occuring in the High latitude F-layer ionosphere. It is shown that magnetic shear reduces the growth rate of these instabilties. The magnetic shear induced stabilization is more effective at the larger scale sizes ($\geq$ tens of kilometers) while at the scintillation causing intermediate scale sizes ($\sim$ a few kms), the growth rate is largely unaffected. The eigen mode structure is localised about a rational surface due to finite magnetic shear and has broken reflectional symmetry due to centroid shift of the mode by equilibrium parallel flow or current.