Analyses of Voyager 2 Plasma Observations in the Heliosheath: Near the Heliospheric Current Sheet and Streamer Belt

摘要

The Voyager plasma experimenters reported that Voyager 2 (V2) in the heliosheath at 99 AU and 30° South measured a large plasma density increase in mid-2012, the culmination of a gradual density increase that commenced in early 2011. This mid-2012 plasma density increase of more than a factor of two was accompanied by an increase in plasma temperature of 50%. They reported that the magnitude of the plasma radial speed remained constant. The Voyager plasma experimenters attributed the changes in plasma density and temperature to increased solar wind pressure resulting in the outward motion of the termination shock. In contrast we attribute these heliosheath plasma characteristics primarily to the heliospheric current sheet (HCS) approaching and crossing the location of V2. Our explanation implies that V2 entered the region associated with the HCS and at times V2 was in the region associated with the solar streamer belt located even closer to the solar equator than the HCS. Near the Sun the HCS and these solar mid-latitude features are often associated with plasma that has higher density and lower speed than the plasma associated with the polar coronal holes. We also analyzed V2 energetic particle data which appeared to substantiate our suggestion that at this time V2 entered the mid-latitude HCS/solar streamer belt region.