Test of the MV method with the Lunquist’s FR without expansion (ζ = 0). The simulated data are defined within the time interval where B_z, FR ≥ 0. Panel a shows the results for MV0 (MV applied to B) and panel b for MV1 (MV applied to ). The FR axis is oriented with i = 90° and λ = 0° so that the simulated observed and FR frames are the same (Fig. 1). Left column: θ_x, θ_y, θ_z are the angles in degrees between the x, y, z directions, respectively, of the FR and MV frames. Middle left column: Δi and Δλ quantify the difference of axis orientations between the FR and the one found by MV, so the orientation biases. Middle right column: ratios of the eigenvalues eν_min, eν_int and eν_max. Right column: ratio of the maximum values of B_z, MV to B_z, FR (amplified by a factor of 100 for the first ratio). The horizontal dotted lines and the yellow regions are landmarks set at the same locations in different figures for the graphs with the same quantities for a better comparison due to the different scales.