Spectrum of the electron density fluctuations: preliminary results from Ulysses observations

Abstract

Ulysses in-situ measurements have given a new picture on the large-scale properties of the fast solar wind as well as on the microscopic scales. From the large sample of data obtained during Ulysses fast latitudinal scans in 1994 and 2007 occuring both near solar minima, we will present the spectrum of the electron density fluctuations. The preliminary analysis suggests that a single Kolmogorov-type power law spectrum does not fit the data at high latitudes in contrast to the ecliptic observations: the spectrum appears to flatten in the high-frequency range of the inertial domain. We will discuss and compare these results and compute the probability distribution functions (for a timescale spanning from a solar rotation to two minutes), based on the use of Wavelet transforms on Ulysses electron density from the URAP experiment. We show as well an evidence of intermittence nature of the electron density fluctuations.