The simplest way to describe what both probes are currently travelling through is as a grouping of frothy magnetic bubbles. NASA is also referring to the area as the “foam zone.” The bubbles are not small, with each measuring around 100 million miles wide.
The foam zone was entered in 2007 by Voyager 1 and 2008 by Voyager 2. The reason we are only now hearing the details is because scientists had no idea what it was both probes were travelling through. A couple of years later and NASA believe they have worked it out.