Monday, 07/24: Writing a pm-code - AIP

PM: main code blocks 20
Density Assignment
The Particle Mesh algorithms assume that particles have certain size, mass,
shape, and internal density. This determines the interpolation scheme used to
assign densities to grid cells. Let’s define the 1D particle shape, S(x), to be
mass density at the distance x from the particle for cell size ∆x (Hockney &
Eastwood 1981). The common choices are
• Nearest Grid Point (NGP): particles are point-like and all of particle’s mass
is assigned to the single grid cell that contains it:
S(x) = 1 ( x
)
∆x δ ∆x
• Cloud In Cell (CIC): particles are cubes (in 3D) of uniform density and of one
grid cell size.
S(x) = 1 {
1, |x| <
1
2 ∆x
∆x 0, otherwise