Maps of B and E modes (panels a and b, respectively) for the model shown in Fig. 3. Panel c: Pearson coefficients between Stokes I (T) and E–B mode maps within the contours shown in panel b, or the 5% brightest pixels of Stokes I. The data points show the mean of 100 random rotations of the filament-magnetic-field system with respect to the LOS. The shadows represent the 1-σ error of the 100 rotations. Regardless of the point of view of the observer with respect to the filament, helical magnetic fields wrapped around filamentary structures do not produce any B-mode signal correlated with the filament in Stokes I (see main text for details).