Statistical analysis of the magnetic fluctuations in boundary layers of Earth’s magnetosphere

Abstract

Investigation of statistical features of the magnetic fluctuations in boundary layers of Earth’s magnetosphere and plasma of the solar wind, on different time scales, is carried out using magnetic field measurements from Cluster-II with a sampling frequency of 22.5Hz in 2007–2010. We have studied the changes of shape and parameters of probability density function for magnetic fluctuations in the solar wind, foreshock region, postshock region and magnetosheath.In particular, the evolution of maximum of probability density function and the structure functions of different orders as characteristics of turbulent processes for different time scales are investigated. Structure functions of high orders are used to determine the character of turbulent processes and the resulting diffusion in these regions. We have found that the highest intermittency is observed in the postshock region. Furthermore, magnetic turbulence in the middle magnetosheath corresponds to log-Poisson turbulent cascade model, and that in the SW plasma conforms to the Iroshnikov–Kraichnan’s model.