Multiscale structure of magnetic fields in the heliosheath

Abstract

Voyager 1 (V1) crossed the termination shock, leaving the solar wind and entering the heliosheath. This paper analyzes the magnetic field observed in the heliosheath from day of year 1 to 308, 2005. The average of the magnetic field strength B is 0.104 nT, but it is highly variable, and its profile appears filamentary. Some sectors and sector boundaries were observed. The daily and hourly averages of B in the inner heliosheath have Gaussian distributions. The widths of the daily and hourly distributions of B are the same within the uncertainties, consistent with a scale invariance of the distribution of B. The distributions of daily and hourly averages of the azimuthal and elevation angles in the heliosheath resemble those in the solar wind. The magnetic field strength in the inner heliosheath has a multifractal structure on scales from ∼2 to 16 days. The multifractal structure can be described by a binomial multiplicative cascade model. The multifractal spectrum of the magnetic field fluctuations in the heliosheath is narrower than that in the distant solar wind. The intermittency exponent decreases by a factor of 3.4 from 0.072 in the distant solar wind to 0.021 in the heliosheath. We also analyzed the multiscale structure of B(t) using wavelets. On an intermediate scale, the magnetic field of the heliosheath contains a quasiperiodic variation suggesting that the effect of solar rotation was observed in the heliosheath beyond 95 AU.