  PSR J1420-6048 is a young gamma-ray pulsar with recurrent glitches. Utilizing
long-term monitoring data obtained from the Fermi Gamma-ray Space Telescope, we
found that PSR J1420-6048 has shown gamma-ray flux variation and we also
detected four glitches between 2008 and 2019. Two of the glitches are
previously unknown, and their gamma-ray spectrum also shows variability between
each glitch. Since the results might be contaminated by background sources, we
discuss whether the observed changes in flux and spectra were caused by
artificial misallocations of photons from a nearby pulsar wind nebula (HESS
J1420-607) and a pulsar (PSR J1418-6058), or a change of the emission geometry
from the target pulsar itself. We examine the correlation of the flux changes
and the alternating pulse structure to investigate whether the emission
geometry in the outer magnetosphere was changing. By assuming the observational
features were not totally resulted from the background environment, we compare
our results with similar phenomena observed in other gamma-ray pulsars and
propose that a strong crust crack can cause timing anomaly of a neutron star,
which can affect the particle accelerations or pair creation regions resulting
in the changes of emission behaviors.
