Radial evolution of the intermittency of density fluctuations in the fast solar wind
- National Institute for Astrophysics, Institute for Space Astrophysics and Planetology, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy)
- National Institute for Astrophysics, Astrophysical Observatory of Torino, Via Osservatorio 20, I-10025 Pino Torinese (Italy)
- Department of Physics, University of Calabria, Via Ponte P. Bucci Cubo 31/C, I-87036 Rende (Italy)
- Department of Physics, University of L'Aquila, Via Vetoio Località Coppito, I-67100 L'Aquila (Italy)
We study the radial evolution of the intermittency of density fluctuations in the fast solar wind. The study is performed by 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 timescales 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 the fast wind are rather intermittent and their level of intermittency, together with the amplitude of intermittent events, decreases with the distance from the Sun, at odds with the intermittency of both magnetic field and all 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.
- OSTI ID:
- 22356986
- Journal Information:
- Astrophysical Journal, Vol. 786, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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