Ion wakes in two-dimensional complex plasma crystals

Ion wakes in two-dimensional complex plasma crystals play a crucial role in determining the structural and dynamical properties of these strongly coupled systems. Using the DRIAD molecular dynamics code [L. S. Matthews, et al., Phys. Plasmas 27, 023703 (2020)], we investigate the formation and morphology of ion wakes beneath a hexagonal cluster of 19 microparticles under two limiting conditions: a collision-less ion flow and an electric-field-driven collisional flow. Our simulations reveal that, in both regimes, individual wakes form downstream of each microparticle, but their shape and intensity differ significantly. Collision-less flows produce elongated wakes with moderate ion-density enhancement, whereas collisional flows generate shorter, more concentrated wakes due to ion-neutral collisions. A striking feature observed in both cases is the emergence of a collective ion-density enhancement beneath the entire cluster, accompanied by a measurable increase in electric potential (up to ∼ 0.5-0.6 V).