3.5.2. Pitfalls of the BSS model

The bisymmetric magnetic field models as applied to the pulsar RM data and to the QSO and galaxies data have many problems in trying to explain the Milky Way galaxy. These are due to the many pitfalls in model fitting the magnetic field reversals observed in the Milky Way (e.g., Vallée 1996b; Sofue & Fujimoto 1983). The magnetic field strength does not go to zero in a spiral arm, as predicted there. Magnetic field reversals in BSS models are numerous but are not periodic. Magnetic field reversals are not due to the twisting of a primordial extragalactic magnetic field. Magnetic field reversals cannot be masked effectively by local interstellar magnetized shells. The prediction of a large number (N >> 4) of magnetic field reversals by the bisymmetric magnetic field models, for spiral arms with pitch angles < 20°, is incompatible with the observations in the Milky Way of at most a small number (N 3) of magnetic field reversals. Thus the strength and sense of the magnetic field with galactic radius (Fig. 8) show that bisymmetric magnetic field models are less suitable to explain the RM data in the Milky Way (e.g., Vallée 1996b).