Magnetic Fields Observed by Voyager 2 in the Heliosheath

Abstract

We present observations of the magnetic field in the outermost region of the heliosheath made by Voyager 2 (V2) from 2016 to 2018.6, just before V2 entered the magnetic barrier inside of the heliopause. The average magnetic field strength (B) during this interval was relatively large, 0.135 nT, mainly due to numerous merged interaction regions. Sector structure was observed, and the direction of azimuthal angle λ was primarily close to the Parker spiral magnetic field directions 90° and 270°. Thus, the heliospheric current sheet extended to relatively high southern latitudes poleward of V2 (>30°). On smaller scales, distributions of daily increments in B and the components of from 2016 to 2018.6 were accurately described by q-Gaussian distributions. The average values of the nonextensivity parameter q for one-day increments of the components decreased from q = 1.7 ± 0.01 during 2016 (near solar maximum) to q = 1.3 ± 0.1 during 2017 and 2018, as solar activity declined. The BT direction was close to the average magnetic field direction, and V2 measured primarily compressible fluctuations. These new results are also presented in the context of an overview of the observations of the magnetic field in the heliosheath from the termination shock crossing to the heliopause.