Ulysses Spacecraft Flies Over Sun's North Pole
- From: baalke@xxxxxxxxxxxxx
- Date: Mon, 14 Jan 2008 17:22:34 -0800 (PST)
http://www.jpl.nasa.gov/news/news.cfm?release=2008-004
Ulysses Spacecraft Flies Over Sun's North Pole
Jet Propulsion Laboratory
January 14, 2008
The Ulysses spacecraft today is making a rare flyby of the sun's north
pole. Unlike any other spacecraft, Ulysses is able to sample winds at
the sun's poles, which are difficult to study from Earth.
Ulysses has flown over the sun's poles three times before, in 1994-95,
2000-01 and 2007. Last week, solar physicists announced the first
indications of a new solar cycle. Visiting the pole at this time may
lead to new insights about solar activity.
"This is a wonderful opportunity to examine the sun's north pole
within
a transition of cycles," said Arik Posner, Ulysses program scientist
at
NASA Headquarters in Washington. "We've never done this before."
Many researchers believe the sun's poles are central to the 11-year
ebb
and flow of solar activity. When sunspots break up, their decaying
magnetic fields are carried poleward by vast currents of plasma. This
makes the poles a sort of graveyard for sunspots. Old magnetic fields
sink beneath the polar surface 200,000 kilometers deep (about 124,000
miles), all the way down to the sun's inner magnetic dynamo, which
generates the solar magnetic field. There, dynamo action amplifies the
fields for use in future solar cycles.
"Just as Earth's poles are crucial to studies of terrestrial climate
change, the sun's poles may be crucial to studies of the solar cycle,"
said Ed Smith, Ulysses project scientist at NASA's Jet Propulsion
Laboratory, Pasadena, Calif.
Each previous flyby revealed something interesting and mysterious. One
puzzle has been the temperature of the sun's poles. In the previous
solar cycle, the magnetic north pole was about 80,000 degrees
Fahrenheit
(more than 44,000 degrees Celsius), or 8 percent cooler than the
south.
The current flyby may help solve this puzzle because it comes less
than
a year after a similar south pole flyby in Feb. 2007. Mission
scientists
will be able to compare temperature measurements, north versus south,
with hardly any gap between them.
Ulysses also discovered the sun's high-speed polar wind. At the sun's
poles, the magnetic field opens up and allows solar atmosphere to
stream
out at a million miles per hour. By flying around the sun, covering
all
latitudes in a way that no other spacecraft can, Ulysses has been able
to monitor this polar wind throughout the solar cycle and has found
that
it is acting a bit odd.
"Twelve years ago, just before the previous 'sea change' between solar
cycles, the polar wind spilled down almost all the way to the sun's
equator. But this time it is not. The polar wind is bottled up,
confined
to latitudes above 45 degrees, " said Posner.
Launched in Oct. 1990 from the space shuttle Discovery, Ulysses is a
joint mission of NASA and the European Space Agency.
More information about NASA's Ulysses mission is available at
http://ulysses.jpl.nasa.gov
------------------------------------------------------------------------
Media contact: DC Agle/JPL
818-393-9011
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