The radially disturbing magnetic field generated by an octopole configuration is Fourier analysed and its impact on the transport processes of the plasma in the boundary region of TEXTOR (a=50 cm) is assessed. The Fourier analysis showed that beyond the radius r=42 cm a magnetically mixed layer is established, where the overlapping of the islands corresponding to each resonant Fourier component is good. As the main figure of merit concerning the transport process, the mean inclination angle epsilon (r) of the field lines against the toroidal direction, is computed. For the coil current Jc=60 kA the maximum value of epsilon (r) is 2.10-3. For TEXTOR, with and without additional heating, the modelling of the boundary region shows that the magnetic limiter action reduces the edge temperatures by a factor 6, and 1.7, respectively, mainly because of the enhanced heat diffusivities. The recycled hydrogen flux is increased roughly by a factor 3, thereby enhancing the electron density at the limiter edge by around a factor 1.6.