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.

The Formation of Magnetic Depletions and Flux Annihilation Due to Reconnection in the Heliosheath

“…At irregular intervals within the magnetic depressions are long-lived pairs of magnetic islands where the magnetic field direction reverses so that spacecraft data would reveal sharp magnetic field depressions with only occasional crossings with jumps in magnetic field direction. This is typical of the magnetic field data from the Voyager spacecraft (Burlaga & Ness 2011;Burlaga et al 2016). Voyager 2 data reveals that fluctuations in the density and magnetic field strength are anti-correlated in the sector zone as expected from reconnection but not in unipolar regions.…”

Voyager 1/UVS Lyman α Measurements at the Distant Heliosphere (90–130 AU): Unknown Source of Additional Emission

“…It is supposed (Burlaga & Ness, ; Gurnett et al, ; Stone et al, ) that in 2012 Voyager 1 crossed the second boundary, that is, the heliopause (HP, tangential discontinuity separating the solar wind plasma from the charged component of the interstellar plasma) and entered the interstellar medium. Voyager 2 is still in the inner heliosheath region (between TS and HP) and approaching the heliopause (Burlaga et al, ; Richardson & Decker, ).…”

Mirror Mode Junctions as Sources of Radiation

“…Similarly one expects that the heliosheath region behind the heliospheric termination shock evolves into magnetic turbulence where the mirror mode will constitute its lowest frequency contribution. The flow speed of the solar wind will become reduced to values similar to the magnetosheath, while the magnetic field drops to B ≈ 0.14 nT, as expected roughly by two orders of magnitude (Burlaga et al, 2016;Fichtner et al, 2020). The unknown length scale will partially compensate for this drop.…”