Rivelazione di oscillazioni ed eventi intermittenti per grandi tempi scala nella corona esterna da parte di UVCS/SOHO

Density fluctuations of the low and midlatitude solar coronal plasma are analyzed during the latest solar minimum period. Long time series of the intensity of the neutral hydrogen Lyα, 1216 Å, line have been observed with the UltraViolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO), at 1.7 Rs, in low-latitude streamers and in regions where the solar wind is accelerated, in order to search for periodic oscillations in the outer corona and intensity fluctuations of the UV emission.The investigation on periodicities and on the presence of persistent and coherent structures in the solar plasma, in order to explore for a possible connection between the plasma oscillations in the outer corona and the convection dynamics in the photosphere, has been carried out by means of three different techniques, the Fourier analysis, the Hurst analysis (based on structure functions) and the Hada analysis (based on phase coherence index).Subsequently, I applied new analysis techniques to the UVCS data, in order to identify and locate intermittency and its properties: Non ¿ gaussian processes analysis ( probability density functions, flatness, skewness);Wavelet transform analysis.The aim of this analysis is to discover the source of intermittency and establish whether or not it might be coronal, hence giving further information on the solar atmospheric layer from which the perturbing material comes.