  We construct evolutionary models of Trappist-1 in which magnetic fields
impede the onset of convection according to a physics-based criterion. In the
models that best fit all observational constraints, the photospheric fields in
Tr-1 are found to be in the range 1450-1700 G. These are weaker by a factor of
about 2 than the fields we obtained in previous magnetic models of two other
cool dwarfs (GJ65A/B). Our results suggest that Tr-1 possesses a global
poloidal field which is some one hundred times stronger than in the Sun. In the
context of exoplanets in orbit around Tr-1, the strong poloidal fields on the
star may help to protect the planets from the potentially destructive effects
of coronal mass ejections. This, in combination with previous arguments about
beneficial effects of flare photons in ultraviolet and visible portions of the
spectrum, suggests that conditions on Tr-1 are not necessarily harmful to life
on a planet in the habitable zone of Tr-1.
