Authors: Hasith Perera(West Virginia University),Paul Cassak(West Virginia University),Hasan Barbhuiya(West Virginia University), Michael Shay(University of Delaware),Greg Howes(University of Iowa),James Juno(PPPL),Jason M. TenBarge(Princeton University),Emily Lichko (University of Chicago)

Landau damping is one of the proposed mechanisms for plasma heating in the solar wind. During Landau damping, the energy stored in the electric field is converted into particle energy through a resonant interaction.It is a well-studied phenomenon that has been identified in a wide range of plasma environments including space observations and laboratory experiments. The velocity space signatures of Landau damping have been studied using modern diagnostics such as the field-particle correlation (Klein and Howes, ApJL, 826, L30, 2016). In this study, we revisit Landau damping of collisionless Langmuir waves using a new suite of entropy diagnostics developed as part of a non-perturbative, first principles approach that quantifies all higher order moments of the phase space density (Cassak et al., PRL, 130, 085201, 2023) to quantify the non-local thermodynamic equilibrium (non-LTE) effects. We use a 1D-1V particle-in-cell (PIC) simulation of a traveling electrostatic Langmuir wave to study the changes in the spatially integrated entropy and use conservation of entropy to ascertain the kinetic properties of the system at late time. In addition, we investigate the spatial variation of entropy to identify and describe the underlying physics that dominates during the early time and late time phases of Landau damping