Nonlinearity in Electro- and Magneto-statics with and without External   Field
  Due to the nonlinearity of QED, a static charge becomes a magnetic dipole if placed in a magnetic field. Already without external field, the cubic Maxwell equation for the field of a point charge has a soliton solution with a finite field energy. Equations are given for self-coupling dipole moments. Any theoretically found value for a multipole moment of a baryon or a meson should be subjected to nonlinear renormalization. 
T. C. Adorno, Caio Costa, D. M. Gitman and A. E. Shabad
hep-th astro-ph.HE quant-ph