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Science Forum Index » Astro Forum » New Horizons Observes Solar Wind Interactions at Jupiter
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 Posted: Fri Feb 09, 2007 9:12 pm |
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http://pluto.jhuapl.edu/news_center/news/020907.htm
SWAP Observes Solar Wind Interactions at Jupiter
February 9 , 2007
A little over a year since launch, with its sights firmly on Jupiter,
the New Horizons spacecraft is testing its science payload and making
observations as it rounds the planet for a gravity-assist that will
speed its journey to the edge of the solar system. As the spacecraft
approaches the planet, the Solar Wind Around Pluto (SWAP) instrument
is
already generating data that will help resolve puzzling questions
about
the interactions between the solar wind, the million-mile-per-hour
stream of ionized gas flowing out from the Sun, and Jupiter's
magnetosphere, the magnetic bubble that surrounds the planet and
encloses ionized gas.
Quote: From a distance of about 0.4 astronomical unit (one AU is the distance
from the Earth to the Sun, or about 100 million miles) from the
planet,
SWAP, built by Southwest Research Institute, observed an immense
structure of compressed, dense, hot ionized gas that forms in the
solar
wind, called a co-rotating interaction region. These structures form
when solar wind streams that are both fast and slow come out of the
Sun,
and flow out in different directions in response to the rotation of
the
Sun. The fast layers try to overtake the slow layers yet are unable to
flow through them, instead compressing the slow material like a snow
plow and bunching up solar wind to create the co-rotating interaction
region. These regions contain significantly higher densities and
pressures that eventually expand and form discontinuities, or shocks,
in
the solar wind, which spread out and away from the high pressure
regions.
"These solar wind structures collide with the magnetospheres of
planets
and, we believe, cause major variations in their structures," says Dr.
David McComas, SWAP principal investigator and senior executive
director
of the SwRI Space Science and Engineering Division. "Because it has
the
largest magnetosphere in the solar system, the effects of the solar
wind
at Jupiter could have significant implications for all the planets."
Studies of these interactions at Jupiter could help determine how much
of the Jovian magnetosphere and aurora are driven by external
processes,
such as the solar wind, versus internal processes, such as planetary
rotation.
"There's an active debate about how much solar wind variability
affects
what magnetospheric responses we will see at Jupiter," McComas
continues. "Except at Earth, we've never had the opportunity to
simultaneously measure the interactions upstream of a planet as we're
observing its aurora, but the Jupiter encounter will soon change
that."
The team is planning collaborative studies that will combine SWAP data
with imaging and spectroscopic observations of Jupiter's aurora using
the Hubble Space Telescope. The fusion of these data will result in
the
first simultaneous upstream observations of solar wind interactions at
Jupiter as the aurora builds and subsides.
"It's exciting that our approach to Jupiter is already yielding new
insights to our particles and plasma science team. We're eagerly
looking
forward to sampling the plasma particle populations in Jupiter's bow
shock and dusk-side magnetosphere later this month, and then exploring
the terra incognita of Jupiter's deep magnetotail in March, April and
May," says New Horizons mission Principal Investigator Dr. Alan Stern,
also of SwRI.
The Jupiter encounter also will enable SWAP to take measurements
inside
Jupiter's magnetosphere, on an orbit that has never before been
traveled. That orbit will carry the spacecraft deep into the
magnetotail, the portion of the magnetosphere that is pushed away from
the Sun by the flowing solar wind. This route will provide the first
close look at Jupiter's more distant magnetotail.
Built to evaluate the solar wind's interaction with Pluto at about 30
AU
from the Sun, SWAP's sensitivity was successfully decreased at
Jupiter's
relatively close distance of about 5 AU from the Sun to generate these
early results.
New Horizons is the first mission in NASA's New Frontiers program. The
Johns Hopkins University Applied Physics Laboratory in Laurel, Md.,
manages the mission and operates the spacecraft for the NASA Science
Mission Directorate. Southwest Research Institute leads the New
Horizons
science and mission teams from the Tombaugh Science Operations Center
in
Boulder, Colo.
Quote: From a Southwest Research Institute news release. For more
information,
contact Maria Martinez, mmartinez@swri.org . |
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