Ponderomotive forces in unmagnetized plasmas described by Kappa distribution functions

TL;DR

This paper investigates how non-thermal Kappa distribution functions influence the ponderomotive forces in unmagnetized plasmas, revealing that suprathermal particles significantly affect the temporal ponderomotive force and induced magnetization.

Contribution

It provides a detailed analysis of the influence of Kappa distributions on ponderomotive forces and magnetization in unmagnetized plasmas, highlighting the role of suprathermal particles.

Findings

Temporal ponderomotive force depends on suprathermal particles and Kappa index.

Non-thermal effects are negligible for spatial force at non-relativistic velocities.

Induced magnetic field increases as plasma deviates from thermal equilibrium.

Abstract

The Washimi and Karpman ponderomotive interaction due to electromagnetic waves propagation is investigated for unmagnetized plasmas described by a isotropic Kappa distribution. We performed a brief analysis of the influence of the Kappa distribution in the dispersion relations for a low temperature plasma expansion at the lowest order in which the thermal effects are appreciated. The spatial and temporal factor of the ponderomotive force is obtained as a function of the wavenumber, the spectral index $\kappa$ and the ratio between the plasma thermal velocity and the speed of light. Our results show that for unmagnetized plasmas non-thermal effects are negligible for the spatial ponderomotive force when non-relativistic thermal velocities are considered. However, for unmagnetized plasmas the temporal factor of the ponderomotive force appears only due to the presence of suprathermal particles, with a clear dependence on the $\kappa$ index. We have also analysed the role of the non-thermal effect in the induced Washimi and Karpman ponderomotive magnetization and the total power radiated associated with it. We have also shown that the slowly varying induced ponderomotive magnetic field magnitude increases as the plasma moves away from thermal equilibrium.