A Magnetic Pressure Front Upstream of the Heliopause and the Heliosheath Magnetic Fields and Plasma, Observed during 2017

Abstract

Voyager 1 ( V1 ), moving in the interstellar magnetic field, observed an increase in the daily averages of B beginning on day ≈346, 2016, rising to a local maximum on day ≈382, and declining nearly monotonically for the most part until day 720, measured from 2016.0. A pressure front was observed during a ≈35-day interval beginning on day 346, 2016. The pressure front observed by V1 was not a shock, although one might expect it to evolve into a shock. Voyager 2 ( V2 ) observed the distant heliosheath during 2017. The average B in the heliosheath was relatively high, 0.130 nT. The distribution of azimuthal angles had two nearly equal maxima at approximately 90° and 180°. An unusual transition of the BT component from a large “away” sector to a large “toward” sector occurred during 2017 from day 101 to day 239. Abrupt but small changes in magnetic polarity occurred between day 146 and day 239, when the average BT component of B was close to zero. Changes in the >70 MeV nucleon −1 cosmic-ray intensity were qualitatively related to the B ( t ) profile described by the CR-B relationship. There was no net decrease in magnetic flux at V2 in the heliosheath during 2017 that might be attributed to ongoing magnetic reconnection in the heliosheath. Small-scale increments in B can be described by a q -Gaussian distribution with q  = 1.64 ± 0.02 for hourly averages of B and q  = 1.54 ± 0.08 for daily averages of B .