sigma Ori E: The Archetypal Rigidly Rotating Magnetosphere

I review the basic concepts of the Rigidly Rotating Magnetosphere model for the circumstellar plasma distribution around the helium-strong star sigma Ori E. I demonstrate that the model can furnish a good fit to the photometric, spectroscopic and magneticv ariability exhibited by this star, and argue that the variability of other helium-strong stars may be amenable to a similar interpretation.