[Table of Contents]

Plasma and Fusion Research

Volume 9, 3401083 (2014)

Regular Articles

TOKI Compression for Plasma Particle Simulations
Katsumi HAGITA, Hiroaki OHTANI1), Tsunehiko KATO2) and Seiji ISHIGURO1)
National Defense Academy, 1-10-20 Hashirimizu, Yokosuka 239-8686, Japan
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
(Received 19 December 2013 / Accepted 28 April 2014 / Published 10 June 2014)


We propose a TOKI (Time Order, Kinetic, and Irreversible) compression method for recording smooth trajectories of particles from PIC (electromagnetic particle-in-cell) simulations. In a TOKI compression, instead of storing entire time sequences of particle positions, we store particle trajectories in terms of coefficients of approximating polynomials. In the current implementation, these coefficients are determined either by the least-squares method or by the Chebyshev approximation formula to obtain quasi-minimax polynomials. In this paper, we present the technique of TOKI compression and compare it with other lossy compression schemes, such as XTC. Comparisons are made using data from a PIC simulation for 150,000 electrons and 150,000 ions. For smooth trajectories, the compression ratio by TOKI is better than that by the XTC format. However, for ballistic trajectories, the compression ratio by TOKI is not good because of the significant overhead in storing raw values of trajectories. We also found that the compression efficiency for ion trajectories is better than that for electron trajectories. This is attributed to different characteristic time scales of motions due to the difference in mass. We expect that the behavior of the compression ratio in TOKI can be used to characterize motions of plasma particles.


TOKI compression, plasma particle simulation, visualization, smooth animation

DOI: 10.1585/pfr.9.3401083


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This paper may be cited as follows:

Katsumi HAGITA, Hiroaki OHTANI, Tsunehiko KATO and Seiji ISHIGURO, Plasma Fusion Res. 9, 3401083 (2014).