  We present the characteristics of the X-ray variability of stars in the
cluster NGC2516 as derived from XMM-Newton/EPIC/pn data. The X-ray variations
on short (hours), medium (months), and long (years) time scales have been
explored. We detected 303 distinct X-ray sources by analysing six EPIC/pn
observations; 194 of them are members of the cluster. Stars of all spectral
types, from the early-types to the late-M dwarfs, were detected. The
Kolmogorov-Smirnov test applied to the X-ray photon time series shows that, on
short time scales, only a relatively small fraction (ranging from 6% to 31% for
dG and dF, respectively) of the members of NGC2516 are variable with a
confidence level $\geq$99%; however, it is possible that the fraction is small
only because of the poor statistics. The time X-ray amplitude distribution
functions (XAD) of a set of dF7-dK2 stars, derived on short (hours) and medium
(months) time scales, seem to suggest that medium-term variations, if present,
have a much smaller amplitude than those on short time scales; a similar result
is also obtained for dK3-dM stars. The amplitude variations of late-type stars
in NGC2516 are consistent with those of the coeval Pleiades stars. Comparing
these data with those of ROSAT/PSPC, collected 7-8 years earlier, and of
ROSAT/HRI, just 4-5 years earlier, we find no evidence of significant
variability on the related time scales, suggesting that long-term variations
due to activity cycles similar to the solar cycle are not common among young
stars. Indications of spectral variability was found in one star whose spectra
at three epochs were available.
