Results of the 3D circularly polarized Alfvén wave test. Top panel: transverse component of the magnetic field in the direction of propagation after five periods. The analytical/initial solution is plotted in black, and the simulation results with resolution [n_x, n_y, n_z]=[128, 74, 78] in red, [n_x, n_y, n_z]=[64, 36, 39] in green, and [n_x, n_y, n_z]=[32, 18, 18] in blue. Both of these are with Wendland C4 kernel with 200 neighbours. Bottom panel: convergence study for the Alfvén wave test using different kernels and neighbour numbers. Shows how the L₁ error scales with resolution (particles along the x-axis). The code default (Wendland C4 kernel with 200 neighbours) is shown in green, Wendland C4 kernel with 114 neighbours are shown in magenta, Quintic kernel with 114 neighbours are shown in blue and the dashed brown line shows the curve for second order convergence. Convergence towards the analytical solution for all kernels are close to second order. When the smoothing length becomes comparable to half the wave length of the Alfvén wave, the MHD gradients becomes more ill defined which causes the slower convergence speed for the Wendland kernel () at low resolution.