Indian research team uses supercomputer to track microscopic mechanisms of turbulence in dusty plasmas

Researchers at the Indian Institute of Technology Jammu (IIT Jammu), in collaboration with the Indian Institute of Technology Kanpur (IIT Kanpur), used supercomputer simulations to study the origin of chaos in dusty plasmas. By tracking the motion of millions of individual particles, the study revealed how turbulent energy is transferred from large-scale vortices to microscopic thermal motion of particles, providing a new computational perspective for nuclear fusion plasma research and astrophysical process analysis.

Plasma is often referred to as the fourth state of matter. Unlike solids, liquids, and gases, atoms in plasma are ionized, forming a system composed of positively charged ions and negatively charged electrons. When tiny solid dust particles enter the plasma, these particles absorb electrons and become negatively charged, subsequently undergoing complex interactions with surrounding particles to form dusty plasma.

In strongly coupled dusty plasmas, the interactions between dust particles are strong, and particles cannot pass freely like ordinary gas molecules but instead exhibit responses similar to elastic media. The researchers noted that such systems can form complex vortex motions and gradually convert ordered motion into heat, inducing mixing and turbulence. For nuclear fusion devices, similar processes may interfere with plasma heating, making it more difficult to achieve the high temperatures required for fusion reactions.

The research team focused on analyzing two types of instabilities commonly found in fluids: the Kelvin—Helmholtz instability and the Rayleigh—Taylor instability. The former typically occurs when two layers of fluid slide relative to each other at different velocities, similar to the process of wind creating ripples on the sea surface; the latter appears when a heavier fluid is situated above a lighter fluid, where interfacial perturbations are rapidly amplified.

To capture the microscopic evolution of these instabilities, the researchers conducted molecular dynamics simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). This tool can track the motion of individual particles in dusty plasmas and identify the critical stage at which large-scale vortex energy begins to break down into microscopic particle motion.

The simulation results showed that before the system reaches thermal equilibrium, energy transfer follows specific mathematical laws; the stronger the coupling between dust particles, the slower the process of energy conversion from large-scale motion to thermal motion. Under strong coupling conditions, the delay in heating and mixing causes the plasma to exhibit behavior resembling elastic turbulence.

The researchers believe that traditional fluid equations such as the Navier—Stokes equations typically treat matter as a continuous medium and struggle to directly describe energy dissipation at the particle scale. This simulation reconstructed continuum behavior from the motion of a large number of particles, helping to bridge microscopic particle dynamics and macroscopic fluid mechanics, and providing a reference for modeling complex plasma systems.

In addition to nuclear fusion research, these findings can also be applied to understanding astrophysical and geophysical processes. The Rayleigh—Taylor instability is closely related to energy transfer in phenomena such as supernova explosions and volcanic eruptions, and the related simulation methods are expected to help researchers analyze how energy evolves and dissipates in these systems.

The research team also noted that the current simulations are still limited to two-dimensional space, whereas most physical processes in reality occur in three-dimensional environments. Although dusty plasmas can exhibit two-dimensional organizational features at small scales, the researchers plan to conduct three-dimensional simulations in future work. The findings have been published in Philosophical Transactions A.