HELIOSHEATH MAGNETIC FIELD AND PLASMA OBSERVED BY VOYAGER 2 DURING 2012 IN THE RISING PHASE OF SOLAR CYCLE 24

Abstract

We discuss magnetic field and plasma observations of the heliosheath made by Voyager 2 ( V2 ) during 2012, when V2 was observing the effects of increasing solar activity following the solar minimum in 2009. The average magnetic field strength B was 0.14 nT and B reached 0.29 nT on day 249. V2 was in a unipolar region in which the magnetic polarity was directed away from the Sun along the Parker spiral 88% of the time, indicating that V2 was poleward of the heliospheric current sheet throughout most of 2012. The magnetic flux at V2 during 2012 was constant. A merged interaction region (MIR) was observed, and the flow speed increased as the MIR moved past V2 . The MIR caused a decrease in the >70 MeV nuc −1 cosmic-ray intensity. The increments of B can be described by a q -Gaussian distribution with q  = 1.2 ± 0.1 for daily averages and q  = 1.82 ± 0.03 for hour averages. Eight isolated current sheets (“PBLs”) and four closely spaced pairs of current sheets were observed. The average change of B across the current sheets was a factor of ≈2, and B increased or decreased with equal probability. Magnetic holes and magnetic humps were also observed. The characteristic size of the PBLs was ≈6 R L , where R L is the Larmor radius of protons, and the characteristic sizes of the magnetic holes and humps were ≈38 R L and ≈11 R L , respectively.