Solar wind turbulence at 0.72 AU and solar minimum
arXiv:1505.05413 · doi:10.1088/2041-8205/804/2/L41
Abstract
We investigate Venus Express (VEX) 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 the solar cycle 24. The Power Spectral Densities (PSD) of the magnetic field components have been computed for the time intervals that satisfy data integrity criteria and have been grouped according to the type of wind, fast and slow defined for speeds larger and respectively smaller than 450 km/s. The PSDs show higher levels of power for the fast than for the slow wind. 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 slow and fast wind.
References in corpus (12)
- Spectrum of magnetohydrodynamic turbulence
- Anisotropic scaling of magnetohydrodynamic turbulence
- Solar Wind Turbulence and the Role of Ion Instabilities
- Spectral energy dynamics in magnetohydrodynamic turbulence
- Dependence of solar wind power spectra on the direction of the local mean magnetic field
- Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind
- Radial Dependence of the Frequency Break Between Fluid and Kinetic Scales in the Solar Wind Fluctuations
- Anisotropy of Alfvénic Turbulence in the Solar Wind and Numerical Simulations
- Residual Energy Spectrum of Solar Wind Turbulence
- Spectral Slope Variation at Proton Scales from Fast to Slow Solar Wind
- On the origin of the 1/f spectrum in the solar wind magnetic field
- Aging of anisotropy of solar wind magnetic fluctuations in the inner heliosphere