2005 年 81 巻 11 号 p. 944-948
A new simulation method that improves the conservation properties of δf particle simulation for the collisionless Boltzmann equation is presented. When the distribution function is divided into a reference distribution specified in advance and a variation distribution, the time evolution of the variation distribution is described by an advection term in the phase space and a source term associated with the reference distribution. The time evolution of the Klimontovich distribution function of the δf method was investigated. It is shown that the errors in the Monte Carlo estimate of the source term in the δf method deteriorate the conservation properties. In the new simulation method, errors in the Monte Carlo estimate of the source term are corrected with a complementary fluid model. An example of the complementary fluid model is presented for bump-on-tail instability. The simulation results are compared with those of the conventional δf method. It is demonstrated that particle, momentum, and energy are well conserved with the new simulation method.
