Abstract
Abstract. Magnetospheric cusps are regions which are characterized by highly turbulent plasma. We have used Polar magnetic field data to study the structure of turbulence in the cusp region. The wavelet transform modulus maxima method (WTMM) has been applied to estimate the scaling exponent of the partition function and singularity spectra. Their features are similar to those found in the nonlinear multifractal systems. We have found that the scaling exponent does not allow one to conclude which intermittency model fits the experiment better. However, the singularity spectra reveal that different models can be ascribed to turbulence observed under various IMF conditions. For northward IMF conditions the turbulence is consistent with the multifractal p-model of fully developed fluid turbulence. For southward IMF experimental data agree with the model of non-fully developed Kolmogorov-like fluid turbulence.
Highlights
A region just outside and/or at the near-cusp magnetopause that is characterized by strong and persistent magnetic turbulence is known as the turbulent boundary layer (TBL) (Savin et al, 1998, 1999, 2002a, b; Pickett et al, 2002)
We have investigated the scaling properties of magnetic field fluctuations as measured in the turbulent boundary layer
We have found that their features are similar to those found in the nonlinear multifractal systems
Summary
A region just outside and/or at the near-cusp magnetopause that is characterized by strong and persistent magnetic turbulence is known as the turbulent boundary layer (TBL) (Savin et al, 1998, 1999, 2002a, b; Pickett et al, 2002). Magnetic turbulence in TBL is dominated by, albeit weak, random-like fluctuations with smooth, continuous spectrum, which cannot be adequately studied with the bi-spectral, or even tri-spectral analysis. In this case we have to resort to more sophisticated methods of data analysis, which make use of the higher order statistics. The power spectrum, being related to a second moment of the probability distribution function (PDF), fully describes fluctuations if they have a Gaussian PDF. In this case, the turbulence is scale-invariant and self-similar.
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