Evolution Of Charged Grains In Harmonic Force Field

Dusty plasma is composed of electrons,ions,neutral molecules and massive dust particles and is also called dusty plasma.It widely exists in celestial bodies and industrial manufacturing industry.Carrying out the research on the dynamic influence of the external harmonic force field on the dusty plasma has very important scientific significance for the development of multiple areas and the interdisciplinary.The dynamic characteristics of charged grains with applying the weak external force and removing the external force after steady state in the dusty plasma system are studied by molecular dynamics numerical simulation method,combined with Newton equation of motion of charged grains and periodic boundary conditions.The spatial structure evolution and vibration properties at a quasi-stationary state are numerically simulated and static structure factors and velocity auto-correlation functions are calculated.The modified Yukawa interaction potential,which includes repulsion and attraction potentials,describes the interaction between the dust charged grains in the background electron and ions.The configuration evolution and motion properties of dusty plasmas in a quasi-steady state can be significantly changed by the external potential field.Charged grains attract each other to form clusters,and then clusters merge with neighboring clusters.Even if the external force is highly asymmetric in the radial direction,the charged grains eventually form a circular distribution of the crystal phase in the center.In the quasi-steady state,each grain performs periodic simple harmonic vibration near its equilibrium position.As the strength of the external force increases,the time to reach the quasi-steady state will also decrease.Finally,the static structure factor is calculated to analyze the properties of the crystal clusters in the quasi-steady state,and the velocity autocorrelation function is employed to further analyze the correlation properties between the charged grains during the spatial structure evolution.The evolution and dynamics of charged grains in dusty plasma change dramatically after the weak space-dependent external force removed.The crystals perform synchronous vibration in the direction of the external force in the first quasi-stable state.After the external force is completely removed,with the size unchanged,the circular cluster starts to move in the direction of the initial external force,until it reaches the second quasi-stable state.The charged grains stop moving and rotate around the center of the cluster.As the external force increases,the time to reach the second quasi-steady state will also increase.