5.11 Interpolate the field to particle markers

As discussed in Sec. 3, for the spatial shape of markers given by the zero-order b-spline function b₀, the corresponding interpolate function is b₁, which corresponds to a simple linear interpolation. Suppose the location of a marker, r_p, is between x_j and x_j+1, then the electric field on the marker is given by

(117)