# Kinetic simulations of ladder climbing by electron plasma waves

## TL;DR

This paper uses nonlinear Vlasov-Poisson simulations to study ladder climbing of electron plasma waves, showing plasmons survive spectrum transformations and are more efficiently driven on BGK waves due to reduced damping.

## Contribution

It provides the first nonlinear simulation-based investigation of ladder climbing in bounded plasma, confirming theoretical predictions and highlighting the role of nonlinear effects in enhancing efficiency.

## Key findings

- Plasmons survive spectrum transformations until Landau damping triggers their destruction.
- Ladder climbing is more effective on BGK waves than on Langmuir waves.
- Nonlinear effects reduce damping, improving ladder climbing efficiency.

## Abstract

The energy of plasma waves can be moved up and down the spectrum using chirped modulations of plasma parameters, which can be driven by external fields. Depending on whether the wave spectrum is discrete (bounded plasma) or continuous (boundless plasma), this phenomenon is called ladder climbing (LC) or autoresonant acceleration of plasmons. It was first proposed by Barth \textit{et al.} [PRL \textbf{115}, 075001 (2015)] based on a linear fluid model. In this paper, LC of electron plasma waves is investigated using fully nonlinear Vlasov-Poisson simulations of collisionless bounded plasma. It is shown that, in agreement with the basic theory, plasmons survive substantial transformations of the spectrum and are destroyed only when their wave numbers become large enough to trigger Landau damping. Since nonlinear effects decrease the damping rate, LC is even more efficient when practiced on structures like quasiperiodic Bernstein-Greene-Kruskal (BGK) waves rather than on Langmuir waves \textit{per~se}.