[meteorite-list] STEREO Sees Solar Hurricane Detach Comet Tail (Comet 2/P Encke)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 1 Oct 2007 14:28:27 -0700 (PDT)
Message-ID: <200710012128.OAA01248_at_zagami.jpl.nasa.gov>

Oct. 1, 2007

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov<

Laura Spector/Nancy Neal Jones
Goddard Space Flight Center, Greenbelt Md.
301-286-0918/0039
laura.a.spector at nasa.gov, nancy.n.jones at nasa.gov

RELEASE: 07-214

NASA SATELLITE SEES SOLAR HURRICANE DETACH COMET TAIL

GREENBELT, Md. - A NASA satellite has captured the first images of a
collision between a comet and a solar hurricane. It is the first time
scientists have witnessed such an event on another cosmic body. One
of NASA's pair of Solar Terrestrial Relations Observatory satellites,
known as STEREO, recorded the event April 20.

The phenomenon was caused by a coronal mass ejection, a large cloud of
magnetized gas cast into space by the sun. The collision resulted in
the complete detachment of the plasma tail of Encke's comet.
Observations of the comet reveal the brightening of its tail as the
coronal mass ejection swept by and the tail's subsequent separation
as it was carried away by the front of the ejection. The researchers
combined the images into a movie.

"We were awestruck when we saw these images," says Angelos Vourlidas,
lead author and researcher at the Naval Research Laboratory,
Washington. "This is the first time we've witnessed a collision
between a coronal mass ejection and a comet and the surprise of
seeing the disconnection of the tail was the icing on the cake."

Encke's comet was traveling within the orbit of Mercury when a coronal
mass ejection first crunched the tail then ripped it completely away.
The comet is only the second repeating, or periodic, comet ever
identified. Halley's comet was the first.

Scientists at the Naval Research Laboratory made the observations
using the Heliospheric Imager in its Sun Earth Connection Coronal and
Heliospheric Investigation telescope suite aboard the STEREO-A
spacecraft. The results will be published in the Oct. 10 issue of the
Astrophysical Journal Letters.

Coronal mass ejections are violent eruptions with masses greater than
a few billion tons. They travel from 60 to more than 2,000 miles per
second. They have been compared to hurricanes because of the
widespread disruption they can cause when directed at Earth. These
solar hurricanes cause geomagnetic storms that can present hazards
for satellites, radio communications and power systems. However,
coronal mass ejections are spread over a large volume of space,
mitigating their mass and power to create an impact softer than a
baby's breath.

Scientists have been aware of the disconnection of the entire plasma
tail of a comet for some time, but the conditions that lead to these
events remained a mystery. It was suspected that coronal mass
ejections could be responsible for some of the disconnected events,
but the interaction between a coronal mass ejection and a comet never
had been observed.

Preliminary analysis suggests the disconnection likely is triggered by
what is known as magnetic reconnection, in which the oppositely
directed magnetic fields around the comet are crunched together by
the magnetic fields in the coronal mass ejection. The comet fields
suddenly link together, reconnecting, to release a burst of energy
that detaches the comet's tail. A similar process takes place in
Earth's magnetosphere during geomagnetic storms, powering the aurora
borealis and other phenomena.

Comets are icy leftovers from the solar system's formation billions of
years ago. They usually reside in the cold, distant regions of the
solar system. Occasionally, the gravitational tug from a planet,
another comet or a nearby star sends a comet into the inner solar
system, where the sun's heat and radiation vaporizes gas and dust
from the comet to form its tail. Comets typically have two tails: one
of dust and a fainter one of electrically conducting gas called
plasma.

"Even though STEREO is primarily designed to study coronal mass
ejections, particularly their impact on Earth, we hope this impact
will provide many insights to scientists studying comets," said
Michael Kaiser, STEREO project scientist at NASA's Goddard Space
Flight Center, Greenbelt, Md.

STEREO is the third mission in NASA's Solar Terrestrial Probes
program, sponsored by NASA's Science Mission Directorate, Washington.
Goddard manages the mission, instruments, and science center. The
Heliospheric Imager was built in the United Kingdom by Rutheford
Appleton Laboratory and the University of Birmingham with major
contributions from the Naval Research Laboratory and the Centre
Spatial de Liege, Belgium. Other international partners in the STEREO
mission include the European Space Agency and France, Germany,
Hungary and Switzerland.

For more information and the related images, visit:

http://www.nasa.gov/stereo

        
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Received on Mon 01 Oct 2007 05:28:27 PM PDT