Magnetic Field Strength Distribution in Interplanetary Turbulence

T. Hartlep, W. H. Matthaeus, N. S. Padhye and C. W. Smith

Journal of Geophysical Research, in press, 1999.

Abstract:

The distribution of magnetic field magnitudes is derived for the special case of a constant mean field and uncorrelated components having Gaussian distributions. Of the three cases considered -- isotropic, transverse, and axisymmetric, the latter most closely resembles a lognormal distribution, when the parallel variance is less than the perpendicular variance. Thus, a normally distributed, non-intermittent vector field can produce a magnitude distribution that closely resembles a functional form often associated with models of intermittency. This result is illustrated by comparison with a magnetic field magnitude distribution computed from the 1 AU Omni dataset. The parameters of the Gaussian component magnitude distribution can be chosen to compare with the data which is also well fit as a lognormal type. We conclude that the magnitude distribution may not be a sensitive indicator of intermittency, and that further examination of the sensitivity of such indicators is warranted.