High resolution measurements of magnetic field fluctuations associated with transitions in solar wind parameters

摘要

Fluctuations in the solar wind parameters and in the heliospheric magnetic field have been studied extensively. The nature of fluctuations has been shown to depend on the origin of the solar wind. However, the regions of transition between the high-speed and the slow speed streams have not been investigated with high resolution. In this work we use high resolution magnetic field measurements on the Ulysses spacecraft to calculate the variances of the fluctuations in the magnetic field components and its magnitude over several timescales, concentrating on intervals of rapid change in the solar wind parameters. At the same time, we computed the cross helicity to assess the Alfvenicity of the fluctuations and changes in it during transitions. The strong variability of all those parameters seems to indicate a filamentary nature of the heliospheric medium.