  Until a few years ago, the amplitude variation in the photometric data had
been limitedly explored mainly because of time resolution and photometric
sensitivity limitations. This investigation is now possible thanks to the
Kepler and CoRoT databases which provided a unique set of data for studying of
the nature of stellar variability cycles. The present study characterizes the
amplitude variation in a sample of main--sequence stars with light curves
collected using CoRoT exo--field CCDs. We analyze potential stellar activity
cycles by studying the variability amplitude over small boxes. The cycle
periods and amplitudes were computed based on the Lomb-Scargle periodogram,
harmonic fits, and visual inspection. As a first application of our approach we
have considered the photometric data for 16 CoRoT FGK main sequence stars,
revisited during the IRa01, LRa01 and LRa06 CoRoT runs. The 16 CoRoT stars
appear to follow the empirical relations between activity cycle periods
($P_{cyc}$) and the rotation period ($P_{rot}$) found by previous works. In
addition to the so-called A (active) and I (inactive) sequences previously
identified, there is a possible third sequence, here named S (short-cycles)
sequence. However, recovery fractions estimated from simulations suggest that
only a half of our sample has confident cycle measurements. Therefore, more
study is needed to verify our results and Kepler data shall be notably useful
for such a study. Overall, our procedure provides a key tool for exploring the
CoRoT and Kepler databases to identify and characterize stellar cycle
variability.
