Anomalous thermal relaxation in warm ion plasmas

ABSTRACT We perform microscopic simulations of the thermal relaxation of warm neutral plasmas of astrophysical importance. Using molecular dynamics we study the thermal relaxation of a hot neutral fluid of finite-size neutron-rich ions kept in a fixed-wall cool box. We show how the interplay among particle size, Yukawa interaction range, and density are key to understand the features of the time-dependent thermal relaxation curve $T(t)$. We show that, under certain conditions, these systems exhibit faster cooling from increasingly larger initial temperature values. They also display non-Newtonian thermal behaviour, including oscillations, that can be effectively interpreted as the consequence of the existence of a non-trivial system memory function. Finally, we consider the impact of multicomponent admixtures in the simulated system. We discuss these results and their possible extensions to astrophysical scenarios, where screened plasmas with Yukawa-like electrostatic potentials are usually involved.