UA Scientists Study Voyager 2's Plunge Through the Heliosphere

FROM: Lori Stiles (520-626-4402, lstiles@xxxxxxxxxxxxx)

UA SCIENTISTS STUDY VOYAGER 2'S PLUNGE THROUGH THE HELIOSPHERE

- December 10, 2007

For the second time in history, a spacecraft still communicating with
Earth
has reached the solar system's final frontier, a vast region at the
edge of
our solar system where the solar wind smashes into the thin gas
between the
stars.

NASA's Voyager 2 probe crossed the solar-wind "termination shock" on
Aug.
30, 2007, which is 30 years and 10 days after the spacecraft launched
from
Cape Canaveral, Fla.

Voyager 2 has been flying out of the solar system in a different
direction
than Voyager 1 and was about 10 billion miles away from the place
along the
termination shock that Voyager 1 crossed on Dec. 17, 2004.

Voyager 2 was also almost a billion miles closer to the sun when it
crossed
the shock, confirming that the heliosphere is asymmetric rather than
spherical. The heliosphere is the bubble carved in interstellar space
by
energetic, charged particles streaming out from the sun.

Scientists, including those from The University of Arizona, are
talking
about it today at the 2007 fall meeting of the American Geophysical
Union in
San Francisco, Calif.

UA Regents' Professor J. Randy Jokipii, Associate Professor Joe
Giacalone
and others in a group at the Lunar and Planetary Laboratory use
advanced
computer models to study energetic particles at astrophysical shock
waves.

At today's meeting, Jokipii presented results on what energetic
particles
observed upstream of the solar-wind termination shock just prior to
the
Voyager spacecraft crossings suggest about the nature of the
termination
shock.

"Termination shocks are not unique to the heliosphere," Jokipii said.
"You
can see one in water running in your kitchen sink. The streaming water
initially radiates outward faster than waves can propagate through it.
As a
result, the surrounding fluid cannot send an inward signal that its
motion
has been slowed. A shock front forms where the fast- and slow-moving
parts
of the fluid abruptly collide."

Jokipii and UA physicist K.C. Hsieh produced a movie that shows the
termination shock created by water flowing from a tap.

The Voyager spacecraft have confirmed that the termination-shock
boundary of
our heliosphere, or that part of space dominated by the solar wind,
like its
water analog, is indeed irregular and turbulent.

"The Holy Grail for me will be when the spacecraft begin traveling in
pure
interstellar space," Jokipii said. "That's maybe 10 years away.
Scientists
now can start thinking about what they want to look for when the
Voyagers
break through the last barriers to true interstellar space."

SCIENCE CONTACT:
J. Randy Jokipii (cell 520-203-2720; 520-621-4256
jokipii@xxxxxxxxxxxxxxx)
.

Relevant Pages