MULTIFRACTAL STRUCTURE OF THE MAGNETIC-FIELD AND PLASMA IN RECURRENT STREAMS AT 1-AU

This paper demonstrates the existence of multifractal structure in the fluctuations of the magnetic field strength, temperature, and density in the recurrent flows at 1 AU. The multifractal scaling is observed over the range of periods from 2 hours to 32 hours for the magnetic field and density and from 2 hours to 16 hours for the temperature. The lower cutoff of 2 hours is related to the use of hour averages; it does not have physical significance. The upper cutoff of 32 hours (16 hours) represents the transition to the mesoscale regime in which the fluctuations are determined by the stream structure. Thus the multifractal structure represents fluctuations superimposed on the corotating stream profile and the heliospheric plasma sheet profile. One may think of the multifractal structure as a texture superimposed on the mesoscale profiles, the structure of the texture being related to the mesoscale structure itself. The multifractal structure of the magnetic field strength fluctuations might be produced by a multiplicative process involving the velocity fluctuations.