  Motivated by indirect observational evidence for strongly magnetized
accretion discs around black holes, and the novel theoretical properties of
such solutions, we investigate how a strong magnetization state can develop and
persist. To this end, we perform local simulations of accretion discs with an
initially purely toroidal magnetic field of equipartition strength. We
demonstrate that discs with zero net vertical magnetic flux and realistic
boundary conditions cannot sustain a strong toroidal field. However, a magnetic
pressure-dominated disc can form from an initial configuration with a
sufficient amount of net vertical flux and realistic boundary conditions. Our
results suggest that poloidal flux is a necessary prerequisite for the
sustainability of strongly magnetized accretion discs.
