  We analyze the long-term lightcurve of 3C 454.3 observed with Fermi/LAT and
investigate its relation to the flux in the radio, optical, and X-ray bands. By
fitting the 1-day binned GeV lightcurve with multiple Gaussian function (MGF),
we propose that the typical variability timescale in the GeV band is 1--10
days. The GeV flux variation is accompanied by the spectral variation
characterized as flux-tracking, i.e., "harder when brighter". The GeV flux is
correlated with the optical and X-ray fluxes, and a weak correlation between
gamma-ray flux and radio flux is also observed. The gamma-ray flux is not
correlated with the optical linear polarization degree for the global
lightcurves, but they show a correlation for the lightcurves before MJD 56000.
The power density spectrum of the global lightcurve shows an obvious turnover
at ~7.7 days, which may indicate a typical variability timescale of 3C 454.3 in
the gamma-ray band. This is also consistent with the derived timescales by
fitting the global lightcurve with MGF. The spectral evolution and an increase
of the optical linear polarization degree along with the increase of the
gamma-ray flux may indicate that the radiation particles are accelerated and
the magnetic field is ordered by the shock processes during the outbursts. In
addition, the nature of 3C 454.3 may be consistent with the self-organized
criticality system, similar to Sagittarius A, and thus the outbursts are from
plasmoid ejections driven by magnetic reconnection. This may further support
the idea that the jet radiation regions are magnetized.
