Evolution of Multipolar Magnetic Field in Isolated Neutron Stars

The evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. We find that except for multipoles of very high order (l\gsim 25) the evolution is similar to that of a dipole. Therefore no significant evolution is expected in pulse shape of isolated radio pulsars due to the evolution of the multipole structure of the magnetic field.Comment: 4 pages, including 4 figures, accepted for publication M.N.R.A.