If a magnetic dipole is formed by taking a "north pole" and a "south pole", bringing them closer and closer together but keeping the product of magnetic pole charge and distance constant, the limiting field is H ( r ) = 1 4 π π [ 3 r ^ ^ ( r ^ ^ ⋅ ⋅ m ) − − m | r | 3 − − 4 π π 3 m δ δ ( r ) ] .