  This work focus on the first results on the identification and
characterization of periodic plasma density fluctuations in the outer corona,
observed in STEREO-A COR1 white-light image time series. A 2D reconstruction of
the spatial distribution and temporal evolution of the coronal fluctuation
power has been performed over the whole plane of the sky, from 1.4 to 4.0 solar
radii. The adopted diagnostic tool is based on wavelet transforms. This
technique, with respect to the standard Fourier analysis, has the advantage of
localizing non-persistent fluctuating features and exploring the variations of
the relating wavelet power in both space and time. The map of the variance of
the coronal brightness clearly outlines intermittent, spatially coherent
fluctuating features, localized along, or adjacent to, the strongest magnetic
field lines. In most cases they do not correspond to the coronal structures
visible in the brightness maps. The results obtained provide a scenario in
which the solar corona shows quasi-periodic, non-stationary density variations
characterized by a wide range of temporal and spatial scales and strongly
confined by the magnetic field topology. In addition, structures fluctuating
with larger power are larger in size and evolve more slowly. The characteristic
periodicities of the fluctuations are comparable to their lifetimes. This
suggests either that plasma fluctuations lasting only one or two wave periods
and initially characterized by a single dominant periodicity, rapidly decay
into a turbulent mixed flow via nonlinear interactions with other plasma modes,
or that they are damped by thermal conduction. [...]
