  We investigate the dynamics of plasma-based acceleration processes with
collisionless particle dynamics and non negligible thermal effects. We aim at
assessing the applicability of fluid-like models, obtained by suitable closure
assumptions applied to the relativistic kinetic equations, thus not suffering
of statistical noise, even in presence of a finite temperature. The work here
presented focuses on the characterization of pressure anisotropies, which
crucially depend on the adopted closure scheme, and hence are useful to discern
the appropriate thermal fluid model. To this aim, simulation results of
spatially resolved fluid models with different thermal closure assumptions are
compared with the results of particle-in-cell (PIC) simulations at changing
temperature and amplitude of plasma oscillations.
