Time evolution of the helicity variation rates, dH_j/dt and dH_pj/dt (dashed black curves; Eqs. (8) and (19)), of the helicity transfer term, dH_j/dt|_Transf and dH_pj/dt|_Transf (solid red curves; Eqs. (10) and (21)), of the own terms, dH_j/dt|_Own and dH_pj/dt|_Own (solid blue curves; Eqs. (18) and (29)), and of the dissipation terms, dH_j/dt|_Diss and dH_pj/dt|_Diss (solid green curves; Eqs. (9) and (20)) for the convergence simulation (top panels) and for the dispersion peripheral simulation (bottom panels). Left and right panels: evolution of the current carrying helicity, H_j, and volume-threading helicity H_pj, respectively.