  We investigate the temporal relation between the Evershed flow, dot-like
bright features (penumbral grain), the complex magnetic field structure, and
dark lanes (dark core) along bright filaments in a sunspot penumbra. We use a
time series of high spatial resolution photospheric intensity, vector magnetic
field maps, and Doppler velocity maps obtained with the Solar Optical Telescope
aboard the \textit{Hinode} spacecraft. We conclude that the appearance and
disappearance of the Evershed flow and penumbra grains occur at nearly the same
time and are associated with changes of the inclination angle of the magnetic
field from vertical to more horizontal. This supports the idea that Evershed
flow is a result of thermal convection in the inclined field lines. The dark
core of the bright penumbral filament also appears coincidental with the
Evershed flow. However, the dark-cored bright filament survives at least for
10-20 minutes after the disappearance of the Evershed flow. The heat input into
the bright filament continues after the end of heat transfer by the Evershed
flow. This suggests that local heating along the bright filament is important
to maintain the brightness of the bright filament in addition to the heat
transfer by the Evershed flow.
