عنوان مقاله [English]
The electric charge of dust particles plays an important role in the study of laboratory plasma, atmosphere plasma, and interplanetary plasma. Often, dust particles are present naturally in space plasma and some laboratory devices. Sometimes they are added to the system as desired in the laboratory for the production of dusty crystalline plasma or to study the dusty plasma behavior. This type of plasma consists of neutral atoms, ions, electrons, and dust particles. Dust particles are usually made of ice, silica, carbon, metal conductors, with different dielectrics, and their sizes range from a few hundred nanometers to several millimeters. The mass of these particles, in comparison with the electron and ion mass, makes it possible to observe many of the dynamic effects of the dusty plasma over a millisecond or longer. The study of how these particles are charged and the effect of their electrical potentials on the plasma properties, has always been a matter of interest. The dust particles are initially without charge, but after a while, with the collision of the electrons and the ions with the dust layer (most of the particles stick to the dust after contact) they become electrically charged. The behavior of dust particles, electrons, and ions in plasma is different in the presence or absence of a magnetic field, and research in this field is of great interest.
Almost all laboratories use a magnetic field to control the plasma and enclose it. The use of a static magnetic field and a magnetic field caused by electromagnetic waves (variable with location and time) is also common. Theoretical, empirical, and simulated study of dusty plasma has a relatively long history. The use of computer simulation method is very popular due to its vast and inexpensive facilities (compared to empirical experiments).
The code of particle-in-cell (PIC) simulation was used to simulate dusty plasma and the effect of magnetic field on the process of dust particle charging by plasma particles under earth’s atmosphere plasma conditions. The electric field was self-consistently solved from the Poisson equation. Electron-neutral elastic scattering, excitation and ionization processes were modeled by Monte Carlo collision methodology. The effects of the difference in the initial density of the plasma and the different magnetic field were simulated. During dust particle charging, the time to reach saturation and saturation load were compared. It was observed that increasing the magnetic field does not necessarily mean that the charge of the dust particles was increased or that the time to reach the saturated state was reduced. Finding the limit of this field, which certainly depends on the physical properties of the plasma, can be useful in some issues, for example, in earth’s atmosphere or laboratory plasma conditions. It was observed that, depending on the initial density of the plasma, the time to reach the saturated stated varied from 15 nanoseconds to 150 nanoseconds. The time to reach the saturated state is inversely proportional to the initial density of the plasma and the radius of dust particles. Also, the results of this simulation can be used in future simulation models that focus on the transportation of dust particles and their effects on the entire plasma.