Dusty Plasma Dynamics During a Void Instability: Heartbeat Instability

When a three-dimensional dust cloud is present in a plasma, a dust-free region, called void, is usually observed in the plasma centre. Forces involved in the void existence are an inward electrostatic force and an outward ion drag one. Under certain conditions, this force balance can be disturbed and this region exhibits a self-excited unstable behaviour consisting in successive contractions and expansions of its size. This low frequency instability (few Hz), called "heartbeat", is here characterised by various diagnostics: electrical and optical measurements, high-speed video imaging. The results brought to the fore the main features of this instability. Correlations between physical processes in the plasma volume and the dust cloud motion are investigated through experimental results.