Grid effects on the plasma simulation by the finite-sized particle
About the so-called usual models, in which the total momentum is conserved, it is well known that the total energy is not conserved due to the nonuniformity of space caused by spatial grids. It fluctuates and increases in time from a stochastic origin. In order to see the accuracy of the plasma simulations, it is important to evaluate the fluctuation Kg, which is more dominant for small errors during the shorter time. We study its standard deviation in t, σ[Kg], and the correlation time of dKg/K . dt, tauc, about periodic one-dimensional systems, where K is the kinetic energy. The stochastic theory was used to evaluate sigma[Kg]. The scaling law was obtained σ[Kg]/K approximately equal to (2/π)1/2 . eta . [(2M)1/2nslambdaD]-1 . (t τcΩp 2)1/2, where 2M is the number of the grids per one period, ns is the electron density, lambdaD is the Debye length, and Ωp is the plasma angular frequency. The coefficient eta depends on the magnitude of the unphysical grid force of each model. Simulations with the usual models (CIC--PIC, modified SUDS, and method 2/2) support this scaling law. It is found that τc approximately equal to Δt if Δt is sufficiently large, and τc approximately equal to 1/4Δ/vth if Δ/(Δt . vth) greater than 3, where Δt is the time step, Δ is the grid distance, and vth is the thermal velocity of the electron.
- Research Organization:
- Kyoto Univ.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-016781
- OSTI ID:
- 4095813
- Journal Information:
- Journal of Computational Physics, Vol. 19, Issue 2; Other Information: Orig. Receipt Date: 30-JUN-76; ISSN 0021-9991
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
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