Scatter plot of sgn(R)B_θ, FR as a function of RB_z,FR using the median profiles of the SEA of Fig. 6. The variable R is considered negative in the inbound and positive in the outbound in order to separate the two regions. The grey line corresponds to the linear least square fit for the MV (blue points) in the range −0.06 au < R <  0.06 au. The y-intercept (y₀ = 0.3) can be approximated to zero, so that the slope of the linear fit approximates to the twist.