Alfvénic turbulence in high speed solar wind streams as a driver for auroral activity

In addition, we present a preliminary statistical study on the intermittency of Bs (the southward z component of the interplanetary magnetic field) and AE, focusing in particular on their respective extreme events (those events that are located in the tails of the distribution and deviate from Gaussian statistics), for different phases of the solar cycle. In order to recognize the extreme events affecting our statistics, we use a technique, called local intermittency measure (LIM), based on wavelet decomposition. Once we have selected all the extreme events we can measure the elapsed time, or waiting time, between consecutive events and build the relative distribution. Our analysis shows that these distributions are characterized by well-defined power laws which would discard the possibility of uncorrelated events and would suggest the existence of long term correlations typical of turbulent processes. Moreover, we find that these distributions do not depend on the particular phase of the solar cycle considered.