Simulações PIC de plasmas com funções de distribuição de velocidades do tipo Kappa

Abstract

In situ observations of plasma of the interplanetary medium consistently show the presence of particles that have velocity distribution functions with non-thermal tails, and frequently with anisotropies that are not well descrided by Maxwellian or Bi-Maxwellian distribution functions. These observed non-thermal features are usually described by distributions featuring power-law tails, represented by the so called Kappa distributions. In general, the Kappa distribution functions have been used empirically for the realization of fitting observational data. Basically, the theory of plasma wave propagation was developed using Maxwellian velocity distribution functions, the description of plasma by a di↵erent distribution function, can modify the dispersion relation of the normal modes of wave propagation in plasma. In this work, we use one simulation method with use particle in cell - PIC, relativistic to investigate the dispersion relation of normal modes of waves propagation in plasmas that electron populations are described by isotropic and anisotropic Kappa functions. We have modified the code to include the Kappa functions as initial velocity distribution function of the particles, as well as relativistic e↵ects. We perform simulations for nonmagnetized plasmas, where the velocities of the particles follow the forms of isotropic and anisotropic Kappa functions widely used in plasmas in space environment for studies of instabilities processes. The results obtained through the simulations coincide with the theoretical results, and when adopting small values for the spectral index  the emission of the Langmuir mode obtained through PIC simulations occurs for small wavenumber, as the index  increases the emission occurs for larger wavenumber.