Solar Wind Magnetic Field Line Dispersal: Multispacecraft Analysis and Comparison with Theoretical Results

The dominance of the global over the relative, cross-field transport of magnetic field lines (MFLs), up to scales of a couple of hours in the solar wind (SW), has been predicted both theoretically and numerically, in the approximation of self-similar, single-level power spectra of magnetic fluctuations. Here the predictions for the MFL relative cross-field transport or dispersal are tested against the results of in situ data analysis, using 23 yr of field and flow measurements on board ACE and Wind. The theoretical results are confirmed/refined by nonlinear theoretical computations and corrected to include the effects of power-level variability or intermittency. Other than confirming earlier theoretical findings at the separation scales rho between a few x10(10) cm and the large-separation limit, with a ballistic regime followed by decorrelation and transition to diffusion in the (ln rho, theta)-space, the new study reveals two new supradiffusive regimes in ln rho and clock angle theta for the MFL dispersal, distinct from a driftinduced supradiffusion found earlier, and distinct from each other. The first supradiffusion, of the nonlinear computations, is a simple nonlinear effect, which cannot be recovered by data analysis at two spacecraft of fixed separation on the analysis timescale. The second supradiffusion, of the data analysis, is much stronger for rho < few x 10(10) cm than the two previous supradiffusions, and it becomes stronger at shorter separations. It follows the ballistic regime without transition through diffusion and is recovered by multiscale, theoretical estimates. It is a Levy-type supradiffusion, due to the intermittency observed in the SW.

Automated summary

The dominance of the global over the relative, cross-field transport of magnetic field lines has been confirmed by 23 years of in situ data analysis. The study revealed two new supradiffusive regimes in the dispersal of magnetic field lines, one caused by nonlinear effects and the other due to intermittency in the solar wind. These findings provide further insights into the transport processes of magnetic field lines in the solar wind.