Apparently, we are now passing through an area of interstellar space that has a low density of gas hydrogen. If and when we go back into normal density, the effect on the heliopause may be to force it back in towards the Sun, and increase the flux of cosmic waves, with unkown effects.
This is the subject of the Innovative Interstellar Explorer project, written about in this week's New Scientist: http://space.newscientist.com/articl...tep-on-it.html
See also: http://interstellarexplorer.jhuapl.edu/

John