The Heliosheath is the solar wind piles up as it presses outward against the approaching wind in interstellar space. It seems the balance in pressure between Heliopause and interstellar wind causes the solar wind to turn back and flow down the tail of the heliosphere.
PIA22835: Two Interstellar Travelers - Illustration shows plasma flow lines both inside and outside the heliopause. The direction of the solar plasma is different from the direction of the interstellar plasma.
My main concern is the interstellar wind so strong and causes this phenomenon, why wouldn't the Voyager probes go backwards affected by the interstellar wind after they went beyond the
Heliosheath Heliosphere? Or in fact they are gradually slowing down?