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 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 collisionless 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. Collisionless 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).