Inertial Range Turbulence of Fast and Slow Solar Wind at 0.72 AU and Solar Minimum
Journal
Date Issued
2015
Author(s)
Description
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, CNCSUEFISCDI, project No. PN-II-ID-PCE-2012-4-0418. The data analysis was partially performed with the AMDA science analysis system provided by the Centre de Donnes de la Physique des Plasmas (IRAP, Universit Paul Sabatier, Toulouse) supported by CNRS and CNES.
Abstract
We investigate Venus Express observations of magnetic field fluctuations performed systematically in the solar wind at 0.72 Astronomical Units (AU), between 2007 and 2009, during the deep minimum of solar cycle 24. The power spectral densities (PSDs) of the magnetic field components have been computed for time intervals that satisfy the data integrity criteria and have been grouped according to the type of wind, fast and slow, defined for speeds larger and smaller, respectively, than 450 km s-1. The PSDs show higher levels of power for the fast wind than for the slow. The spectral slopes estimated for all PSDs in the frequency range 0.005-0.1 Hz exhibit a normal distribution. The average value of the trace of the spectral matrix is -1.60 for fast solar wind and -1.65 for slow wind. Compared to the corresponding average slopes at 1 AU, the PSDs are shallower at 0.72 AU for slow wind conditions suggesting a steepening of the solar wind spectra between Venus and Earth. No significant time variation trend is observed for the spectral behavior of both the slow and fast wind.
Volume
804
Issue
2
Start page
L41
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...804L..41T
Rights
open.access
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