[This is an erratum applied version to Phys. Rev. Lett. 117, 081603 (2016). The conclusion is not changed, but we should have considered not decreasing but increasing spatial modulations in the magnetic profile.] Using the worldline formalism we compute an effective action for fermions under a temporally modulated electric field and a spatially modulated magnetic field. It is known that the former leads to an enhanced Schwinger Mechanism, while we find that the latter can also result in enhanced particle production and even cause a reorganization of the vacuum to acquire a larger dynamical mass in equilibrium which spatially assists the Magnetic Catalysis.