Threshold phenomena in a throbbing dusty plasma
Résumé
A dust cloud trapped in a plasma often contains a dust-free region ("void") near the plasma center. This void has important effects: it induces a spatial inhomogeneity of the dust particle distribution and is at the origin of many intricate unstable phenomena. One of this behavior is the heartbeat instability consisting of successive contractions and expansions of the void. This instability is characterized by a strong nonlinear dynamics which can reveal the occurrence of incomplete sequences corresponding to failed contractions. Experimental results based on high-speed imaging are presented for the first time and underline this threshold effect in both the dust cloud motion and the evolution of the plasma light emission.