Comparison of the helicity variation rate and the helicity flux computed in the practical DeVore gauge. The helicity variation rate (, dashed line) is derived from the volume-integration method. The total helicity flux through the whole surface, , of the domain is F_tot (red line). This flux is composed of Eqs. (26)−(29): F_Vn (green line), F_Bn (blue line), F_φ (orange line), and F_AAp (purple line).