  We study the emission patterns and light curves of gamma-rays in the pulsar
magnetosphere with a current-induced magnetic field perturbation. Based on the
solution of a static dipole with the magnetic field induced by some currents
(perturbation field), we derive the solutions of a static as well as a retarded
dipole with the perturbation field in the Cartesian coordinates. The static
(retarded) magnetic field can be expressed as the sum of pure static (retarded)
dipolar magnetic field and the static (retarded) perturbation field. We use the
solution of the retarded magnetic field to investigate the influence of the
perturbation field on the emission patterns and light curves, and we apply the
perturbed solutions to calculate the gamma-ray light curves for the case of the
Vela pulsar. We find out that the perturbation field induced by the currents
will change the emission patterns and then light curves of gamma-rays,
especially for a larger perturbation field. Our results indicate that the
perturbation field created by the outward-flowing (inward-flowing) electrons
(positrons) can decrease the rotation effect on the magnetosphere and makes
emission pattern appear to be more smooth relative to that of the pure retarded
dipole, but the perturbation field created by the outward-flowing
(inward-flowing) positrons (electrons) can make the emission pattern less
smooth.
