  Evidence is presented from numerical magneto-hydrodynamical simulations for
the existence of magnetic activity in late-type giant stars. A red supergiant
with stellar parameters similar to that of Betelgeuse (alpha Orionis) is
modeled as a "star-in-a-box" with the high-order "Pencil Code". Both linear
kinematic and non-linear saturated dynamo action are found: the non-linear
magnetic field saturates at a super-equipartition value (a factor two above
equipartition yielding surface fields with strengths on the order of 500
Gauss), while in the linear regime two different modes of dynamo action are
found. It is speculated that magnetic activity of late-type giants may
influence dust and wind formation and possibly lead to the heating of the outer
atmospheres of these stars.
