Formation of Coulomb lattice in a dusty plasma

对过程等离子体和空间等离子体中尘埃粒子的结构形成进行了研究，并进行了数值模拟。我们制作了模拟代码，其中假设尘埃颗粒与汤川型相互作用力相互作用。利用该模拟代码，我们证实了库仑晶格的形成，并与以往的模拟工作进行了比较。此外，我们还开发了一个模拟代码，其中介绍了尘埃颗粒，正离子和电子的动力学，正离子和电子附着在尘埃颗粒上。利用该模拟代码，我们观察到尘埃粒子随着时间的推移带负电荷，并且随着尘埃粒子负电荷的增加而形成库仑晶格。这与实验室等离子体中的库仑晶格形成相对应。然而，由于直接计算粒子、离子和电子之间的相互作用力，这种模拟模型的成本相当高。因此，我们利用PPPM （Particle-Particle-Particle-Mesh）方法开发了高性能的尘埃等离子体模拟代码。该方法直接求解相邻粒子间的相互作用，利用空间网格求解距离较远的粒子间的相互作用。另一方面，我们也进行了PIC （Particle-in-Cell）模拟，模拟了在无碰撞等离子体中由于局部产生重负离子而形成的等离子体结构。我们已经证明，在负离子产生区域产生的负电位结构，间歇性地传播到等离子体流的下游区域。

We have researched structure formation of dust particles in process and space plasmas and made numerical simulation modeling.We made simulation code in which dust particles are assumed to interact with Yukawa type interaction force. Using this simulation code, we have confirmed that the formation of Coulomb lattice and have compared with previous simulation works. Furthermore, we have developed a simulation code in which the dynamics of dust particles, positive ions, and electrons, the attachment of positive ions and electrons to dust particles are introduced. Using this simulation code, we have observed that the dust particles are negatively charged with time and the Coulomb lattice is formed with the increase in negative charge of dust particles. This corresponds to the Coulomb lattice formation in laboratory plasmas. However, this simulation model is quite expensive because the interaction force among particles, ions and electrons are directly calculated. Thus, we have developed high-performance dust plasma simulation code with PPPM (Particle-Particle-Particle-Mesh) method. In this method, the interaction between neighboring particles are directly solved while the interaction between far away particles are solved by using spatial meshes.On the other hand, we have also performed the PIC (Particle-in-Cell) simulation on the formation of plasma structure due to localized generation of heavy negative ions in a collisionless plasma. We have shown that a negative potential structure, which is created in the negative ion production region, propagates intermittently to the downstream region of the plasma flow.