Development and Application of Geospace Environment Simulator for the Analysis of Spacecraft–Plasma Interactions

Abstract

Space development has been rapidly increasing, and a strong demand should arise regarding the understanding of the spacecraft-plasma interactions, which is one of the very important issues associated with the human activities in space. To evaluate the spacecraft-plasma interactions including plasma kinetics, transient process, and electromagnetic field variation, the authors have started to develop a numerical plasma chamber called Geospace Environment Simulator (GES) by making the most use of the conventional full particle-in-cell plasma simulations. For the development of a proto model of GES, the authors have used the Earth Simulator, which is one of the fastest supercomputers in the world. GES can be regarded as a numerical chamber in which space experiments can be virtually performed and temporal and spatial evolutions of spacecraft-plasma interactions can be analyzed. In this paper, the authors have briefly introduced GES in terms of its concept, modeling, and research targets. As one of the research topics of GES, the authors have investigated the impedance variation of electric field antenna onboard scientific satellites in the photoelectron environment in space. From the preliminary simulation results, the large change of reactance of the antenna impedance below the characteristic frequency corresponding to the local plasma frequency determined by the photoelectron density could be confirmed.

OhHelp

“…The implementation is based on our production level simulator for space plasma [29], a type of pure PIC code without particleparticle interaction although OhHelp itself is capable of it as discussed later.…”

“…With these notations, it can be shown that particledecomposed simulations [13,17,18,29] are not scalable because P = P but D = D. Since P D in usual cases, a small scale parallel executions are feasible but, even if we have a large local memory to accommodate a large D, the all-reduce communication, which takes O(D log N ) time with butterfly algorithms or O(D + log N ) even with more sophisticated recursive halving/doubling techniques [26], should make parallel performance saturated as shown in Section 4.2.…”

“…These proposals and successors can be projected onto a spectrum whose two extremes are particle decomposition and domain decomposition. In a particle-decomposed simulation [13,17,18,29], the set of simulated particles is statically divided into equal-size subsets each of which assigned to each computation node, while all the nodes share the whole of space domain data associated to grid points. Sharing the domain data is easy and natural for the implementations on shared memory machines and is fairly simple even for distributed memory machines because we just need to distribute the copies of them.…”

Analysis of photoelectron effect on the antenna impedance via Particle‐In‐Cell simulation

“…We have developed a numerical tool for analysis of antenna characteristics in plasma environment by using the electromagnetic PIC (EM‐PIC) plasma simulations [ Usui et al , 2006; Miyake et al , 2008]. In the developed tool, Maxwell's equations for fields and equations of motion for charged particles are solved as basic equations.…”

“…The detailed treatments of fields and particles at the boundaries were presented in the study by Miyake et al [2008]. We also implemented a function that handles electron emission from the conducting surfaces in order to simulate photoelectron emission [ Usui et al , 2006]. The developed method was validated and successfully applied to the impedance analysis of ion‐sheathed antennas under the condition that the Debye length is smaller than the antenna length.…”