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

Detection of plasma fluctuations in white-light images of the outer solar corona: investigation of the spatial and temporal evolution