Magnetic fields in the heliosheath:: Voyager 1 observations

Magnetic fields in the heliosheath were observed by Voyager 1 (V1) from 2004 DOY 352 to 2005 125, when V1 moved from 94.04 to 95.24 AU at 34 degrees.1N. The strongest fields (0.31 nT, observed on 2005 DOY 8-9, occurred in a narrow peak containing very large amplitude fluctuations. This peak was associated with a cusplike minimum in the flux of ions > 0.5MeV. The largest structure observed in the interval was a unipolar magnetic sector, which V1 entered on 2004 DOY 360 and exited on 2005 DOY 110. In the sector, the distribution functions of each of the three components of hour averages of B relative to their mean values were Gaussian; the widths of these distributions were all comparable, indicating that the fluctuations in B were nearly isotropic. The distribution of hour averages of the magnetic field strength B was also Gaussian in the sector. A high-resolution sample of turbulence in the sector shows that the fluctuations in both the magnitude and each of the components of the 48 s averages of B also have Gaussian distributions. The turbulence on this scale is compressible and isotropic relative to the mean B. This sample of the turbulence contains ordered features, including magnetic holes. The leading sector boundary occurred within an 18 hr interval on 2004 DOY 360. The trailing sector boundary occurred within a approximate to 14 hr interval on 2005 DOY 110-111, beginning with a very narrow (approximate to 20 minutes) "D-sheet'' (consistent with magnetic reconnection). Both sector boundaries were associated with large variations in B, including magnetic holes and waves. There was a large, abrupt decrease in B from 0.14 to 0.05 nT across the trailing sector boundary, and a region with low values of B (approximate to 0.05 nT) moved past V1 for more than 15 days following the sector boundary.