Solar Wind Turbulence and Intermittency at 0.72 AU – Statistical Approach

Abstract:

Through this analysis we characterize the turbulent magnetic fluctuations by Venus Express Magnetometer, VEX-MAG in the solar wind during the last solar cycle minimum at a distance of 0.72 AU from the Sun. We analyze data recorded between 2007 and 2009 with time resolutions of 1 Hz and 32 Hz. In correlation with plasma data from the ASPERA instrument, Analyser of Space Plasma and Energetic Atoms, we identify 550 time intervals, at 1 Hz resolution, when VEX is in the solar wind and which satisfy selection criteria defined based on the amount and the continuity of the data. We identify 118 time intervals that correspond to fast solar wind. We compute the power spectral densities (PSD) for B_x, B_y, B_z, B, B², B_|| and B_^. We perform a statistical analysis of the spectral indices computed for each of the PSD's and evidence a dependence of the spectral index on the solar wind velocity and a slight difference in power content between parallel and perpendicular components of the magnetic field. We also estimate the scale invariance of fluctuations by computing the Probability Distribution Functions (PDFs) for B_x, B_y, B_z, B and B² time series and discuss the implications for intermittent turbulence.

Research supported by the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS – UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.