Electron residual energy due to stochastic heating in field-ionized plasma

TL;DR

This paper investigates how stochastic heating in field-ionized plasma leads to residual electron energy, using theoretical models and extensive PIC simulations to analyze the effects of pulse length and scattering mechanisms.

Contribution

It introduces a combined theoretical and simulation approach to study electron residual energy and stochastic heating in field-ionized plasma, highlighting the impact of pulse length and scattering processes.

Findings

Electron residual energy increases with ionization and initial conditions.

Longer pulse lengths enhance stochastic electron motion and scattering effects.

Thomson scattering dominates over Raman scattering with increasing pulse length.

Abstract

The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is here investigated. The optical response of plasma is initially modeled by using the concept of two counter-propagating electromagnetic waves. The solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared to the case without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will significantly be changed by applying a minor change to the initial conditions. Extensive kinetic 1D-3V particle-in-cell (PIC) simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in sufficient long pulse length is high enough to act as a second counter-propagating wave for triggering the stochastic electron motion. On the other hand, the analyses of intensity spectrum reveal this fact that the dominant scattering mechanism tends to Thomson rather Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside the pulse region.