  The complete high-resolution lightcurves of Swift GRB 080319B present an
opportunity for detailed temporal analysis of the prompt optical emission. With
a two-component distribution of initial Lorentz factors, we simulate the
dynamical process of the ejected shells from the central engine in the
framework of the internal shock model. The emitted radiation are decomposed
into different frequency ranges for a temporal correlation analysis between the
lightcurves in different energy bands. The resulting prompt optical and
gamma-ray emission show similar temporal profiles, both as a superposition of a
slow variability component and a fast variability component, except that the
gamma-ray lightcurve is much more variable than its optical counterpart. The
variability features in the simulated lightcurves and the strong correlation
with a time lag between the optical and gamma-ray emission are in good
agreement with the observations of GRB 080319B. Our simulations suggest that
the variations seen in the lightcurves stem from the temporal structure of the
shells injected from the central engine of gamma-ray bursts. The future high
temporal resolution observations of prompt optical emission from GRBs, e.g., by
UFFO-Pathfinder and SVOM-GWAC, provide a useful tool to investigate the central
engine activity.
