Maxwell equations
∇⋅E=ρ, ∇⋅B=0, ∇×E=−∂t∂B, ∇×B=∂t∂E+J. Discrete version:
ΔtEyn+1−Eyn∣∣i+1/2,j,k+1/2=−ΔxBi+1,j,k+1/2−Bi,j,k+1/2∣∣zn+1/2+ΔzBi+1/2,j,k+1−Bi+1/2,j,k∣∣xn+1/2−Jy,i+1/2,j,k+1/2n+1/2, ΔtBzn+1/2−Bzn−1/2∣∣i,j,k+1/2=−ΔxEi+1/2,j,k−Ei−1/2,j,k∣∣yn+ΔyEi+1/2,j+1,k−Ei+1/2,j,k∣∣xn