Transient growth in stable collisionless plasma

TL;DR

This paper investigates how collisionless plasmas can exhibit transient growth despite being linearly stable, using a Landau fluid model to reveal the kinetic origins of non-normality and transient amplification.

Contribution

It presents the first kinetic analysis of transient growth in collisionless plasmas, linking non-normality to kinetic effects and confirming findings with nonlinear simulations.

Findings

Transient growth occurs in stable collisionless plasmas due to non-normality.

Non-normality is more pronounced at smaller scales and higher plasma beta.

Linear spectral theory results are validated by nonlinear simulations.

Abstract

The first kinetic study of transient growth for a collisionless homogeneous Maxwellian plasma in a uniform magnetic field is presented. A system which is linearly stable may display transient growth if the linear operator describing its evolution is non-normal, so that its eigenvectors are non-orthogonal. In order to include plasma kinetic effects a Landau fluid model is employed. The linear operator of the model is shown to be non-normal and the results suggest that the nonnormality of a collisionless plasma is intrinsically related to its kinetic nature, with the transient growth being more accentuated for smaller scales and higher plasma beta. The results based on linear spectral theory have been confirmed with nonlinear simulations.