Structure of the Turbulent Interplanetary Magnetic Field

Abstract

We show that two widely used but apparently different models of the turbulent interplanetary magnetic field are closely related. One of these is the so-called quasi-static turbulence model, in which interplanetary magnetic field fluctuations are generated at a source surface near the Sun by random transverse plasma motions (such as supergranulation at the solar photosphere or perhaps reconnection) and are thereafter carried outward at a uniform constant speed in a radial solar wind. The other model of heliospheric magnetic turbulence is known as the two-component model, in which the random part of the field is decomposed into components along the field (slab fluctuations) and normal to it. Both models have provided us with useful simplified parameterizations of inter-planetary fluctuations, and both enter into calculations that show good agreement with observations. Here we show that by properly choosing the temporal and spatial dependence of the transverse velocity field at the solar source surface in the quasi-static model, we can generate a two-component model (as well as many others). In particular, the anisotropy observed in the turbulence can be incorporated into both models. This study provides us with important insights that increase our understanding of turbulence and energetic particle transport in the heliosphere.