Elsevier, Planetary and Space Science, 15(55), p. 2224-2227
DOI: 10.1016/j.pss.2007.05.022
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Turbulent spectrum of magnetic fluctuations in the solar wind nearly follows Kolmogorov's law ∼f-5/3 below the ion cyclotron frequency fci. 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 fci. 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 fci 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 ∼f-7/3+2α, which depends on the degree of plasma compressibility α.