# Characterizing Fluid and Kinetic Instabilities using Field-Particle Correlations on Single-Point Time Series

## TL;DR

This paper applies a modified field-particle correlation technique to single-point time series from electrostatic simulations to diagnose kinetic instabilities and understand energy transfer mechanisms in plasma systems.

## Contribution

It introduces a modified correlation method suitable for single-point data, enabling analysis of kinetic instabilities in systems where integrated quantities are inaccessible.

## Key findings

- Correlation characterizes physical mechanisms driving instabilities
- Method effectively diagnoses counter-streaming and bump-on-tail instabilities
- Potential application to turbulent magnetized plasmas and solar wind

## Abstract

A recently proposed technique correlating electric fields and particle velocity distributions is applied to single-point time series extracted from linearly unstable, electrostatic numerical simulations. The form of the correlation, which measures the transfer of phase-space energy density between the electric field and plasma distributions and had previously been applied to damped electrostatic systems, is modified to include the effects of drifting equilibrium distributions of the type that drive counter-streaming and bump-on-tail instabilities. By using single-point time series, the correlation is ideal for diagnosing dynamics in systems where access to integrated quantities, such as energy, is observationally infeasible. The velocity-space structure of the field-particle correlation is shown to characterize the underlying physical mechanisms driving unstable systems. The use of this correlation in simple systems will assist in its eventual application to turbulent, magnetized plasmas, with the ultimate goal of characterizing the nature of mechanisms that damp turbulent fluctuations in the solar wind.