Voyager Buffeted by Interstellar 'Tsunami Waves'
 
Dec. 16, 2014:  Since 2012, NASA's Voyager 1 spacecraft has experienced three
'tsunami waves' in interstellar space.  The most recent, which reached the
spacecraft earlier this year, is still propagating outward according to new
data. It is the longest-lasting shock wave that researchers have seen in
interstellar space.
 
"Most people would have thought the interstellar medium would have been smooth
and quiet. But these shock waves seem to be more common than we thought," said
Don Gurnett, professor of physics at the University of Iowa in Iowa City.
Gurnett presented the new data Monday, Dec. 15 at the American Geophysical
Union meeting in San Francisco.
 
https://www.youtube.com/watch?v=_u-RZTwpECg#t=41
 
The Voyager 1 spacecraft has experienced three "tsunami waves" in interstellar
space. Listen to how these waves cause surrounding ionized matter to ring like
a bell.
 
A "tsunami wave" occurs when the sun emits a coronal mass ejection, throwing
out a magnetic cloud of plasma from its surface. This generates a wave of
pressure. 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.
 
"The tsunami causes the ionized gas that is out there to resonate -- "sing" or
vibrate like a bell," said Ed Stone, project scientist for the Voyager mission
based at California Institute of Technology in Pasadena.
 
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.
 
"This remarkable event raises questions that will stimulate new studies of the
nature of shocks in the interstellar medium," said Leonard Burlaga,
astrophysicist emeritus at NASA Goddard Spaceflight Center in Greenbelt,
Maryland, who analyzed the magnetic field data that were key to these results.
 
It is unclear to researchers what the unusual longevity of this particular
wave may mean. They are also uncertain as to how fast the wave is moving or
how broad a region it covers.
 
The second tsunami wave helped researchers determine in 2013 that Voyager 1
had left the heliosphere, the bubble created by the solar wind encompassing
the sun and the planets in our solar system. Denser plasma "rings" at a higher
frequency, and the medium that Voyager flew through, was 40 times denser than
what had been previously measured. This was key to the conclusion that Voyager
had entered a frontier where no spacecraft had gone before: interstellar space.
 
"The density of the plasma is higher the farther Voyager goes," Stone said.
"Is that because the interstellar medium is denser as Voyager moves away from
the heliosphere, or is it from the shock wave itself? We don't know yet."
 
Gurnett, principal investigator of the plasma wave instrument on Voyager,
expects that such shock waves propagate far out into space, perhaps even to
twice the distance between the sun and where the spacecraft is right now.
 
Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both
spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and
Neptune. Voyager 2, launched before Voyager 1, is the longest continuously
operated spacecraft and is expected to enter interstellar space in a few years.
 
Credits and more information:
Production editor: Dr. Tony Phillips | Credit: Science@NASA
 
JPL, a division of Caltech, built the twin Voyager spacecraft and operates
them for the Heliophysics Division within NASA's Science Mission Directorate
in Washington.
 
For more information on the Voyager mission, visit http://voyager.jpl.nasa.gov
 
 
Regards,
 
Roger

--- D'Bridge 3.99
 * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)