Abstract-Ion acoustic (IA) solitons are accompanied by vortex-shaped nonlinear structures (e.g. hollows, plateaus or humps) in the electron distribution function, called electron holes, portraying trapped electrons. These structures appear as charged flexible clouds (shielded by the background plasma) in the phase space with their own inertia, depending on the number of trapped electrons. According to simulation studies, electron holes tend to merge in pairs until one accumulative hole remains in the simulation box. This tendency has been analytically and qualitatively explained in the frame of the energy conservation principle. However, electron holes accompanying IA solitons should not merge due to stability of IA solitons against mutual collisions. In this report based on a fully kinetic simulation approach, detailed study of the collisions of IA solitons reveals the behavior of electron holes under these two conflicting predictions, i.e. stability against mutual collisions and merging tendency. Four main results are reported here. Firstly, we find that among the three different types of collisions possible for electron holes, just two of them happen for electron holes accompanying IA solitons. We present different collisions, e.g. two large/small and large versus small holes, to cover all the these three different types of collisions. Secondly, we show that although electron holes merge during collisions of IA solitons, the stability of IA solitons forces the merged hole to split and form new electron holes. Thirdly, we reveal that holes share their trapped population during collisions. Post-collision holes incorporate some parts of the oppositely propagating before-collision holes. Finally, it is shown that the newly added population of trapped electrons goes through a spiral path inside the after-collision holes hole because of dissipative effects. This spiral is shown to exist in the early stage of the formation of the holes in the context of the IA soliton dynamics.

The propagation of ionic perturbations in a dusty plasma is considered through a three-species kinetic simulation approach, in which the temporal evolution of all three elements i.e. electrons, ions and dust particles are followed based on the Vlasov equation coupled with the Poisson equation. Two cases are focused upon: firstly a fully electron depleted dusty plasma, i.e., a plasma consisting of ions and dust-particles. The second case includes dusty plasmas with large electron-to-ion temperature ratios. The main features of the ionic waves in these two settings including the dispersion relation and the Landau damping rate are studied. It is shown that the dispersion relation of the ionic waves perfectly matches the dispersion relation of Langmuir waves and hence are called Langmuirlike ionic waves and can be considered as Langmuir-like ionic waves. These waves can be theoretically predicted by the dispersion relation of the dust-ion-acoustic waves. The transition of ionic waves from dust-ion-acoustic to Langmuir-like waves are shown to be sharp/smooth in first/second case. The Landau damping rates based on simulation results are presented and compared with theoretical predictions wherever possible.