How can DC-magnetic fields be produced with the aid of currents? What's a possible theoretical explanation for this, and how does one achieve this in the real world? What are the maximum fields that could be produced this way?
Any conductor carrying DC current produces a unidirectional magnetic field. A brief explanation of the phenomenon is given here: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html