Development of Electromagnetic Particle Simulation Code in an Open System

Abstract

In an electromagnetic particle simulation for magnetic reconnection in an open system, which has a free boundary condition, particles go out and come into the system through the boundary and the number of particles depends on time. Besides, particles are locally attracted due to physical condition. Accordingly, it is hard to realize an adequate load balance with domain decomposition. Furthermore, a vector performance does not become efficient without a large memory size due to a recurrence of array access. In this paper, we parallelise the code with High Performance Fortran. For data layout, all field data are duplicated on each parallel process, but particle data are distributed among them. We invent an algorithm for the open boundary of particles, in which an operation for outgoing and incoming particles is performed in each processor, and the only reduction operation for the number of particles is executed in data transfer. This adequate treatment makes the amount and frequency of data transfer small, and the load balance among processes relevant. Furthermore, a compiler-directive listvec in the gather process dramatically decreases the memory size and improves the vector performance. Vector operation ratio becomes about 99.5% and vector length turns 240 and over. It becomes possible to perform the simulation with 800 million particles in 512 × 128 × 64 meshes. We succeed in opening a path for a large-scale simulation.

Open Boundary Condition for Particle Simulation in Magnetic Reconnection Research

“…The free boundary condition of particles is important in constructing the open boundary model [25,26,39]. Although noise problems near the system boundary are inevitable in PIC simulations, we propose an advanced model to reduce the noise.…”

“…Several other types of open boundary models have been proposed thus far for investigating driven or spontaneous reconnection as well [34][35][36][37][38]. In our previous studies [28,31,32,39], we improved the 2-D full PIC simulation code in an open system to a three-dimensional (3-D) code. However, the frozen-in condition is slightly broken at the upstream boundary, and unphysical disturbance is faintly generated at the downstream boundary.…”

Three-dimensional particle simulation on structure formation and plasma instabilities in collisionless driven reconnection

“…This adequate treatment reduces the amount and frequency of data transfer. The compiler-directive line listvec in the gather process dramatically decreases the memory size and improves the vector operation in an NEC SX system (vector operation ratio is about 99.5% and vector length turns 240 and over) [9].…”

“…A variety of plasma instabilities have so far been studied as candidates for an anomalous resistivity in a current sheet [4][5][6][7][8]. To clarify the relationship between particle kinetic effects and anomalous resistivity due to plasma instabilities, we have developed a three-dimensional particle simulation code for magnetic reconnection in an open system 'PASMO' [4,5], in which a distributed parallel algorithm is integrated for a distributed memory and multi-processor vector computer system [9].…”

Scientific Visualization of Magnetic Reconnection Simulation Data by the CAVE Virtual Reality System

“…The initial velocity is given by the Box-Muller method [9] with the same average velocity as the flow velocity, which is given by simulation data. Simulation data of a collisionless driven reconnection is obtained by the 3-D PArticle Simulation code for Magnetic reconnection in an Open system (PASMO) [10][11][12]. The initial condition is given by a one-dimensional Harris-type equilibrium, in which the magnetic field is parallel to the x-axis and a function of the y-coordinate.…”