Boundary induced amplification and nonlinear instability of interchange modes

TL;DR

This paper demonstrates that small boundary distortions in magnetized plasma systems near marginal stability can be significantly amplified and lead to nonlinear instabilities, with boundary effects playing a crucial role in plasma stability.

Contribution

It reveals how boundary distortions can induce nonlinear instability in marginally stable magnetized plasmas, highlighting the sensitivity to boundary conditions.

Findings

Boundary distortions are amplified in the plasma core near marginal stability.

Systems can become nonlinearly unstable due to boundary effects.

Instability can be triggered by fractional boundary distortions of order $b^{3/2}$.

Abstract

It is shown that small distortions on the boundaries are amplified in the core of a magnetized plasma if the system is close to marginal stability for the ideal magnetohydrodynamic interchange mode. It is also shown that such marginal systems can be nonlinearly unstable. The combination of boundary amplification and nonlinearity is shown to result in a nonlinear instability. The induced instability is highly sensitive to the boundary in that, if the fractional deviation from marginality is a small parameter $b$, the system can go unstable from fractional boundary distortions of $\mathcal{O}(b^{3/2})$.