I thought some of you might be interested in this NASA press release..
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73 de KK1L ex N1PBT...ron (rrossi@btv.ibm.com) <><
Ron Rossi H/P SRAM Engineering -- IBM Microelectronics
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Donald Savage
Headquarters, Washington, DC August 28, 1997
(Phone: 202/358-1547) EMBARGOED UNTIL 1 PM EDT
Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-8955)
RELEASE: 97-184
SCIENTISTS DISCOVER MASSIVE JET STREAMS FLOWING INSIDE THE SUN
Scientists using the joint European Space Agency (ESA)/NASA
Solar and Heliospheric Observatory (SOHO) spacecraft have
discovered "jet streams" or "rivers" of hot, electrically charged
gas called plasma flowing beneath the surface of the Sun. They
also found features similar to trade winds that transport gas
beneath the Sun's fiery surface.
These new findings will help them understand the famous
sunspot cycle and associated increases in solar activity that can
affect the Earth with power and communications disruptions. The
observations are the latest made by the Solar Oscillations
Investigation (SOI) group at Stanford University, Palo Alto, CA,
and they build on discoveries by the SOHO science team over the
past year.
"We have detected motion similar to the weather patterns in
the Earth's atmosphere," said Dr. Jesper Schou of Stanford.
"Moreover, in what is a completely new discovery, we have found a
jet-like flow near the poles. This flow is totally inside the
Sun. It is completely unexpected, and cannot be seen at the surface."
"These polar streams are on a small scale, compared to the
whole Sun, but they are still immense compared to atmospheric jet
streams on the Earth," added Dr. Philip Scherrer, the SOI
principal investigator at Stanford. "Ringing the Sun at about 75
degrees latitude, they consist of flattened oval regions about
17,000 miles across where material moves about 10 percent (about
80 mph) faster than its surroundings. Although these are the
smallest structures yet observed inside the Sun, each is still
large enough to engulf two Earths."
Additionally, there are features similar to the Earth's
trade winds on the surface of the Sun. The Sun rotates much
faster at the equator than at the poles. However, Stanford
researchers Schou and Dr. Alexander G. Kosovichev have found that
there are belts in the northern and southern hemispheres where
currents flow at different speeds relative to each other. Six of
these gaseous bands move slightly faster than the material
surrounding them. The solar belts are more than 40 thousand miles
across and they contain "winds" that move about ten miles per hour
relative to their surroundings.
The first evidence of these belts was found more than a decade
ago by Dr. Robert Howard of the Mount Wilson Observatory. The Stanford
researchers have now shown that, rather than being superficial
surface motion, the belts extend down to a depth of at least
12,000 miles below the Sun's surface.
"In one way, the Sun's zonal belts behave more like the
colorful banding found on Jupiter than the region of tradewinds on
the Earth," said Stanford's Dr. Craig DeForest. "Somewhat like
stripes on a barber pole, they start in the mid-latitudes and
gradually move toward the equator during the eleven-year solar
cycle. They also appear to have a relationship to sunspot
formation as sunspots tend to form at the edges of these zones.
"We speculate that the differences in speed of the plasma
at the edge of these bands may be connected with the generation of
the solar magnetic cycle which, in turn, generates periodic
increases in solar activity, but we'll need more observations to
see if this is correct," said DeForest.
Finally, the solar physicists have determined that the
entire outer layer of the Sun, to a depth of at least 15,000
miles, is slowly but steadily flowing from the equator to the
poles. The polar flow rate is relatively slow, about 50 miles per
hour, compared to its rotation speed, about 4,000 miles per hour;
however, this is fast enough to transport an object from the
equator to the pole in a bit more than a year.
"Oddly enough, the polar flow moves in the opposite
direction from that of the sunspots and the zonal belts, which are
moving from higher to lower latitudes," said DeForest.
Evidence for polar flow previously had been observed at the
Sun's surface, but scientists did not know how deep the motion
extended. With a volume equal to about 4 percent of the total
Sun, this feature probably has an important impact on the Sun's
activity, argue Stanford researchers Scherrer, with Dr. Thomas L.
Duvall Jr., Dr. Richard S. Bogart, and graduate student Peter M. Giles.
For the last year, the SOHO spacecraft has been aiming its
battery of 12 scientific instruments at the Sun from a position
930,000 miles sunward from the Earth. The Stanford research team
has been viewing the Sun's surface with one of these instruments
called a Michelson Doppler Imager that can measure the vertical
motion of the Sun's surface at one million different points once
per minute. The measurements show the effects of sound waves that
permeate the interior. The researchers then apply techniques
similar to Earth-based seismology and computer-aided tomography to
infer and map the flow patterns and temperature beneath the Sun's
roiling surface.
"These techniques allow us to peer inside the Sun using
sound waves, much like a doctor can look inside a pregnant woman
with a sonogram," said Dr. Schou.
Currently, the Stanford scientists have both identified new
structures in the interior of the Sun and clarified the form of
previously discovered ones. Understanding their relationship to
solar activity will require more observations and time for analysis.
"At this point, we do not know whether the plasma streams
snake around like the jet stream on Earth, or whether it is a less
dynamic feature," said Dr. Douglas Gough, of Cambridge University,
UK. "It is intriguing to speculate that these streams may affect
solar weather like the terrestrial jetstream impacts weather
patterns on Earth, but this is completely unclear right now. The
same speculation may apply to the other flows we've observed, or
they may act in concert. It will be especially helpful to make
observations as the Sun enters its next active cycle, expected to
peak around the year 2001."
- end -
Images to support this story can be found at the following
Internet address:
http://pao.gsfc.nasa.gov/gsfc/newsroom/flash/flash.htm
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