Channeling and surfing of projectiles in chain-bundle dusty plasma liquids

We investigate experimentally the dynamics of the wake field and the high speed projectile travelling along the channels formed by the surrounding long vertical chains of the chain-bundle dusty plasma liquids (CBDPLs) consisting of negatively charged dusts suspended in weakly ionized low pressure discharges, in which the downward ion flow not only causes the formation of long vertical chains but also can temporarily sustain the downward dust acoustic waves trigged by external perturbations. For the supersonic projectile channeling in the quiescent CBDPL, the excitation of the downward travelling narrow wake field associated with the elliptical motions of the background dusts is observed. The continuous increase and the subsequent oscillation of the drag force on the projectile as the projectile speed goes below the resonant velocity for wave excitation manifest the strong projectile-wake field interaction, especially after the wake field catches up the subsonic projectile. The acceleration and surfing of the projectile through the interaction of the projectile with an existing large amplitude dust acoustic wave excited by the strong external local perturbation are also observed.