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We analyze the long-term lightcurve of 3C 454.3 observed with Fermi/LAT andinvestigate its relation to the flux in the radio, optical, and X-ray bands. Byfitting the 1-day binned GeV lightcurve with multiple Gaussian function (MGF),we propose that the typical variability timescale in the GeV band is 1--10days. The GeV flux variation is accompanied by the spectral variationcharacterized as flux-tracking, i.e., "harder when brighter". The GeV flux iscorrelated with the optical and X-ray fluxes, and a weak correlation betweengamma-ray flux and radio flux is also observed. The gamma-ray flux is notcorrelated with the optical linear polarization degree for the globallightcurves, but they show a correlation for the lightcurves before MJD 56000.The power density spectrum of the global lightcurve shows an obvious turnoverat ~7.7 days, which may indicate a typical variability timescale of 3C 454.3 inthe gamma-ray band. This is also consistent with the derived timescales byfitting the global lightcurve with MGF. The spectral evolution and an increaseof the optical linear polarization degree along with the increase of thegamma-ray flux may indicate that the radiation particles are accelerated andthe magnetic field is ordered by the shock processes during the outbursts. Inaddition, the nature of 3C 454.3 may be consistent with the self-organizedcriticality system, similar to Sagittarius A, and thus the outbursts are fromplasmoid ejections driven by magnetic reconnection. This may further supportthe idea that the jet radiation regions are magnetized.

Flux and Spectral Variation Characteristics of 3C 454.3 at the GeV Band