Speaker
Description
A novel 2D-2V time-splitting Vlasov-Poisson solver has been used to deduce the kinetic behavior of the propagation of high-frequency electrostatic plasma waves in an inhomogeneous electron background. More specifically, we have simulated, in a scenario of constant proton density, the effect of density holes, where a lack of electrons leads to an unbalanced charge. These regions have been recreated by building an equilibrium distribution function for the electrons with a dependence on single-particle energy only. By imposing the cylindrical symmetry of the corresponding density in a periodic spatial domain, we obtain a class of solutions of the Poisson equation with the number of particles vanishing at the center. Choosing a hole at scales around the Debye length, the system is then perturbed by adding the contribution of x-propagating electron acoustic waves (EAWs) in a strong Debye and sub-Debye turbulent regime, where the fluctuation of the second Casimir invariant (enstrophy) has already cascaded towards small scales of the x-vx phase space. The periodic conditions of the system permit the description of the interaction of this turbulent scenario with a lattice of density holes: we observe how the repeated change of phase velocity of EAWs due to density inhomogeneity leads to strong folding and stirring of the distribution function, resulting in the formation of an enstrophy cascade even in the y-vy space. The resulting regime is deeply analyzed through the Fourier analysis of density profiles and the application of the Hermite transform on the velocity distribution at each point in space, to explore the relationship between plasma heating and the formation of small velocity gradients.
