In situ observations of magnetic field fluctuations

Abstract

It is well known that the irregularities of the magnetic field are intimately related to the motion of charged particles. Although transport theories need the spatial and time variations of the magnetic field as input, in situ observations are very limited. Ulysses observations have provided a major step forward by entering the unexplored high latitude regions of the heliosphere, the knowledge of which is vital to interpret particle flux measurements, even at the ecliptic. We analyze the magnetic field data of Ulysses during the mission to study the waves and discontinuities in the heliosphere at different locations, covering a total sunspot cycle. Various tools are employed, including power spectral and structure function analysis. A remarkable difference was found between the fluctuations in the fast and slow solar wind. We argue that the latitudinal extent of the high speed solar wind contributes significantly to the latitudinal variation of the transport parameters, which should also affect the 11 (and 22) year modulation cycle.