Magnetic field strength distribution in interplanetary turbulence

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, nonintermittent 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. Copyright 2000 by the American Geophysical Union.