Reduction of a Ship's Magnetic Field Signatures - Paperbackby John Holmes (Author) Decreasing the magnetic field signature of a naval vessel will reduce its susceptibility to detonating naval influence mines and the probability of a submarine being detected by underwater barriers and maritime patrol aircraft. Both passive and active techniques for reducing the magnetic signatures produced by a vessel's ferromagnetism, roll induced eddy currents, corrosion related sources, and stray fields are presented.