Numerical Simulation Research About Sheath Characteristics In Terminator Region Of Lunar Surface

As the first step of mankind's long and arduous space journey,the moon is an important starting point for mankind to move into space,but what hinders mankind is the dust particles that can be seen everywhere on the moon.Because moondust is electrostatically charged,it can stick to any surface it touches.Moondust is corrosive and can wear the spacesuit and electronic equipment,to cause critical mechanisms to jam and damage the control system.At present,it is mainly believed that electrostatic migration is the primary movement mechanism of moondust.Due to the special plasma environment around the moon,a complicated electric field structure will be formed on the lunar surface,especially in the lunar terminator region.However,there is a lack of research on the characteristics of the sheath in the lunar terminator region.Therefore,the study of the plasma environment and its sheath structure in the lunar terminator region plays a vital role in the migration mechanism of moondust particles.Based on the theory of immersed finite element and particle in cell,a sheath simulation program for the terminator region is established,the electric field environment in the terminator region of the lunar surface is simulated.The simulation results show that the electric potential of the lunar surface transitions from low electric potential in a non-illuminated area to high electric potential in an illuminated area,and the electric field intensity near the boundary line is much greater than that in other areas.The sheath oscillation phenomenon in terminator region is discovered,and the sheath oscillation characteristics in this area are analyzed.The results show that the oscillation frequency of the sheath in terminator region is the same as the plasma oscillation frequency,and the sheath oscillation amplitude in the illuminated area is greater than that in the non-illuminated area.The influence of the solar wind environment parameters on the sheath structure of the terminator region is discussed through the sheath simulation program.Plasma density,electron and photoelectron temperature,photoelectron density will affect the current source in the sheath,which will cause the difference in surface charge on both sides of the terminator region,and affect the sheath structure near the junction.Finally,according to the charging and discharging model of the moondust and the dynamic model,the electrostatic migration of the moondust in the terminator region was simulated.The electrostatic floating characteristics of the charged moondust in the terminator region were discussed.The research results show that the smaller the particle size of the charged moondust near the junction,the higher the flying height,but the horizontal migration distance of different moondust size is not much different under the influence of the horizontal electric field at the junction.