and H_∂𝒱,# evolution in the system computed with different gauges. The left panel has been computed with the practical DeVore method, while the right panel has been derived with the DeVore-Coulomb method. The helicity variation (, black dashed line) is derived from the volume-integration method. The time-integrated helicity is (red line), which can be separated into the contribution of its different terms: (blue line), (green line), (orange line), and (purple line). The orange line in the insets corresponds to the difference between and .