  The Sun and the undisturbed interstellar magnetic field and plasma velocity
vectors (Bis,Vis) define a mirror symmetry plane of the flow at large
heliospheric distances. We show that for the Bis direction defined by IBEX
Ribbon center, the radial direction of Voyager 2 over the last decade, and the
(thermal proton) plasma velocity measured by the spacecraft since 2010.5, are
almost parallel to the (Bis,Vis)-plane, which coincides in practice with the
Hydrogen Deflection Plane. These facts can be simply explained if approximate
mirror symmetry is also maintained on the inner side of the heliopause. Such
approximate symmetry is possible since the solar wind ram pressure is almost
spherically symmetric and the plasma beta value in the inner heliosheath is
high. In the proposed symmetry, the plasma flow speed measured by Voyager 2 in
the inner heliosheath is expected to rotate more in the transverse than in the
polar direction (explanation alternative to McComas & Schwadron (2014)), in
evident agreement with available spacecraft data (our Fig.1).
