Radial evolution of intermittency of density fluctuations in the fast solar wind

Abstract

We study the radial evolution of intermittency of density fluctuations in the fast solar wind. The study is performed analyzing the plasma density measurements provided by Helios 2 in the inner heliosphere between $0.3$ and $0.9$ AU. The analysis is carried out by means of a complete set of diagnostic tools, including the flatness factor at different time scales to estimate intermittency, the Kolmogorov-Smirnov test to estimate the degree of intermittency, and the Fourier transform to estimate the power spectral densities of these fluctuations. Density fluctuations within fast wind are rather intermittent and their level of intermittency, together with the amplitude of intermittent events, decreases with distance from the Sun, at odds with intermittency of both magnetic field and all the other plasma parameters. Furthermore, the intermittent events are strongly correlated, exhibiting temporal clustering. This indicates that the mechanism underlying their generation departs from a time-varying Poisson process. A remarkable, qualitative similarity with the behavior of plasma density fluctuations obtained from a numerical study of the nonlinear evolution of parametric instability in the solar wind supports the idea that this mechanism has an important role in governing density fluctuations in the inner heliosphere.

References in corpus (4)

• Radial evolution of solar wind intermittency in the inner heliosphere
• Intermittency, scaling and the Fokker-Planck approach to fluctuations of the solar wind bulk plasma parameters as seen by the WIND spacecraft
• The role of compressibility in solar wind plasma turbulence
• The clustering of polarity reversals of the geomagnetic field

Cited by in corpus (7)

• Metis: the Solar Orbiter visible light and ultraviolet coronal imager
• Density Fluctuations Associated with Turbulence and Waves: First Observations by Solar Orbiter
• Arbitrary-order Hilbert spectral analysis and intermittency in solar wind density fluctuations
• Helios 2 observations of solar wind turbulence decay in the inner heliosphere
• Isotropic Scaling Features Measured Locally in the Solar Wind Turbulence with Stationary Background Field
• First detection of acoustic-like flux in the middle solar corona
• Statistical study of electron density turbulence and ion-cyclotron waves in the inner heliosphere: Solar Orbiter observations