CANCELLATION EXPONENTS AND MULTIFRACTAL SCALING LAWS IN THE SOLAR-WIND MAGNETOHYDRODYNAMIC TURBULENCE

Some signed measures in turbulence are found to be sign-singular, that is their sign reverses continuously on arbitrary finer scales with a reduction of the cancellation between positive and negative contributi ons. The strength of the singularity is characterized by a scaling exp onent kappa, the cancellation exponent. In the present study by using some turbulent samples of the velocity field obtained from spacecraft measurements in the interplanetary medium, we show that sign-singulari ty is present everywhere in low-frequency turbulent samples. The cance llation exponent can be related to the characteristic scaling laws of turbulence. Differences in the values of kappa, calculated in both hig h- and low-speed streams, allow us to outline some physical difference s in the samples with different velocities.