Searching invisible helical dynamos in a cylinder

An “invisible dynamo” is a dynamo which operates in an electrically conducting region surrounded by vacuum and which generates a magnetic field which is trapped in the electrically conducting region so that no magnetic field exists in the vacuum. Consequently, observations from outside the conducting region are unable to detect this dynamo. The search for an invisible kinematic dynamo is started in an infinite cylinder with periodic boundary conditions along the axis. The first results suggest that invisible magnetic decay modes exist in cylinders, but that no invisible growing field can be supported by the dynamo mechanism.