Spontaneous Convective Patterns in a Dusty Plasma

We present experimental findings on the manifestation of self-sustaining convective patterns in a laboratory dusty plasma system. The dusty plasma is produced by introducing the mono-dispersive Melamine Formaldehyde microspheres in the background of a capacitively coupled radio frequency (RF) Argon discharge. Notably, we observe the spontaneous formation of a pair of convective cells featuring opposing vorticities, evident in a lateral view of the system upon surpassing specific threshold values of background gas pressure and RF power. The effect of various driving mechanisms for the occurrence of such structures, including inhomogeneous plasma density, non-uniform ion drag, and neutral drag, is discussed. The kinetic level measurements from the Particle Tracking Velocimetry (PTV) have unveiled the presence of a dust temperature gradient driving the emergence of the aforementioned counter-rotating patterns. The origin of the kinetic temperature gradient in the dust cloud, in the absence of any external heat source, is attributed to the ion flux induced heating of the lower particles in the cloud. The velocity and vorticity of the particles in the convective cell increase with an increase in the vertical kinetic temperature gradient. The experimental observations are compared with the findings of classical molecular dynamics simulations.