'Tsunami Wave' still being experienced by NASA's Voyager 1 spacecraft

Scientists have revealed that the "tsunami wave" that NASA's Voyager 1 spacecraft began experiencing earlier this year is still propagating outward.

The Voyager 1 spacecraft has experienced three shock waves and the most recent shock wave, first observed in February 2014, still appears to be going on and one wave, previously reported, helped researchers determine that Voyager 1 had entered interstellar space.

Don Gurnett, professor of physics at the University of Iowa in Iowa City, said that most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than they thought.

A "tsunami wave" occurs when the sun emits a coronal mass ejection, throwing out a magnetic cloud of plasma from its surface, which generates a wave of pressure and when the wave runs into the interstellar plasma -- the charged particles found in the space between the stars -- a shock wave results that perturbs the plasma.

This is the third shock wave that Voyager 1 has experienced. The first event was in October to November of 2012, and the second wave in April to May of 2013 revealed an even higher plasma density. Voyager 1 detected the most recent event in February, and it is still going on as of November data. The spacecraft has moved outward 250 million miles (400 million kilometers) during the third event.