Abstract
Around 16th October, 2011, it was detected by the Fermi Large Area Telescope (LAT) that the pulsar PSR J2021+4026 experienced a sudden drop in flux above 100 MeV. At the same time, the pulsar spindown rate and the pulsation profile also changed significantly. It has been widely argued that these changes were related to a shift in the magnetic field structure of the pulsar. To investigate the effect of magnetic structure, in particular, the magnetic inclination and the structure of the charge acceleration region, on the spectrum and light curve of PSR J2021+4026, the three-dimensional two-layer outer gap model (Wang, 2011) was used in the problem.
Using the gamma-ray data obtained from the Fermi LAT, the parameters in the model were adjusted to produce comparable phase-averaged spectrum and light curve.