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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 3
Ann. Geophys., 14, 259–269, 1996
https://doi.org/10.1007/s00585-996-0259-4
© European Geosciences Union 1996
Ann. Geophys., 14, 259–269, 1996
https://doi.org/10.1007/s00585-996-0259-4
© European Geosciences Union 1996

  31 Mar 1996

31 Mar 1996

Multifractal scaling of the kinetic energy flux in solar wind turbulence

E. Marsch, C.-Y. Tu, and H. Rosenbauer E. Marsch et al.

Abstract. The geometrical and scaling properties of the energy flux of the turbulent kinetic energy in the solar wind have been studied. Using present experimental technology in solar wind measurements we cannot directly measure the real volumetric dissipation rate, ε(t), but are constrained to represent it by its surrogate the energy flux near the dissipation range at the proton gyro scale. There is evidence for the multifractal nature of the so defined dissipation field ε(t), a result derived from the scaling exponents of its statistical moments. The generalized dimension Dq has been determined and reveals that the dissipation field has a multifractal structure, which is not compatible with a scale-invariant cascade. The related multifractal spectrum α has been estimated for the first time for MHD turbulence in the solar wind. Its features resemble those obtained for turbulent fluids and other nonlinear multifractal systems. The generalized dimension Dq can for turbulence in high-speed streams be fitted well by the functional dependence of the p-model with a comparatively large parameter p1=0.87, indicating a strongly intermittent multifractal energy cascade. The experimental value for Dp/3 used in the scaling exponent s(p) of the velocity structure function gives an exponent that can describe some of the observations. The scaling exponent μ of the autocorrelation function of ε (t) has also been directly evaluated, being 0.37. Finally, the mean dissipation rate was determined, which could be used in solar wind heating models.

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