"The latest data from Voyager 1 indicate that we are clearly in a new region where things are changing quickly," says Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. This is very exciting. We are approaching the solar system's final frontier."
A telltale sign of the frontier’s approach is the number of cosmic rays hitting Voyager 1. Cosmic rays are high energy particles such as protons and helium nuclei accelerated to near-light speed by distant supernovas and black holes. The heliosphere protects the solar system from these subatomic bullets, deflecting and slowing many of them before they can reach the inner planets. As Voyager approaches the frontier, the number of cosmic rays has gone up.
More at - http://science.nasa.gov/science-news/science-at-nasa/2012/21jun_finalfrontier/