It’s the scientific consensus that, out at the edge of the solar system, Voyager 1 has crossed the termination shock — possibly again — and is now sailing through the heliosheath, the outer layer of our sun’s bubble of influence. That far from the sun, the solar wind “bunches up” as it slows down against the pressure of the interstellar wind, causing an increase in temperature, and in the density of the magnetic field around Voyager.
It’s hoped that the Voyagers will continue operating long enough to reach the heliopause, that point at which the solar wind starts streaming backward into the sun’s wake, and punch through into true interstellar space. More from the Voyager home page about those outer layers.
The earlier probe Pioneer 10, by the way, is flying in the opposite direction, into the heliosphere, the sun’s wake trailing behind it as it moves through the interstellar medium. Sadly, we lost contact with Pioneer 10 in 2003.