Clouds-in-Clouds, Clouds-in-Cells Physics for Many-Body Plasma Simulation

A clouds-interacting-with-clouds, clouds-in-cells method (CIC) is presented for many-body nonlinear plasma problems. Density and force are obtained by assuming that the particles have finite size, are tenuous, and may pass through one another; the particles are thus called clouds. They obey a Coulomb force (~1/ror 1/r3) when separated and a linear force (~r) when overlapping, allowing simple harmonic oscillations at small separation. CIC is contrasted with the zero-size particle and nearest-grid-point approach, ZSP?NGP. CIC appears to have substantially less unwanted noise than ZSP?NGP and should be more useful in simulating dense plasmas. Initial runs have been encouraging. The methods may find use in other many-body simulations, such as with stars, or with particles in phase space.