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Alexandrova Olga, Carbone Vincenzo, Veltri Pierluigi, Sorriso-Valvo L.

Solar wind Cluster observations: Turbulent spectrum and role of Hall effect

Planetary and Space Science, 2007, vol. 55, pp. 2224-2227

Référence DOI : 10.1016/j.pss.2007.05.022
Référence ADS : 2007P&SS...55.2224A

Résumé :

Turbulent spectrum of magnetic fluctuations in the solar wind nearly follows Kolmogorov's law &tilde;f below the ion cyclotron frequency f<SUB>ci</SUB>. Above this frequency, the observed steeper power law is believed to be a 'dissipative range' of the solar wind turbulence. In this paper we analyze magnetic field fluctuations measured onboard Cluster, lasting two decades above f<SUB>ci</SUB>. Well-defined power law and a strong increase of intermittency with frequency in this range indicates that turbulence cannot be characterized by a 'dissipative range'. Rather we conjecture that above f<SUB>ci</SUB> the turbulence is generated by a different nonlinear cascade. We suggest that the presence of dispersive effects is responsible for a steepening of the spectral energy density, simply because a cascade can be realized in a time that is shorter than the usual eddy-turnover time. In the Hall MHD formulation, the magnetic power follows a law &tilde;f, which depends on the degree of plasma compressibility alpha.

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