The Magnetic Switch as the Origin of the FR I/FR II Break

We propose that the Fanaroff & Riley division between class I and class II radio sources has its origins in the coronae of magnetized accretion disks around black holes. The “ magnetic switch”, an effect that critically controls the speed of jets produced by such disks, can explain both qualitative and quantitative differences in the properties of the two classes. These include why morphology and jet speed are functions of radio power and why the division between the two classes is a strong function of galaxy optical luminosity.