Scientists pinpoint the
'edge of space'
Friday, April 10,
2009
Where does space begin? Scientists at the University of Calgary
have created a new instrument that is able to track the transition
between the relatively gentle winds of Earth's atmosphere and the
more violent flows of charged particles in space – flows that can
reach speeds well over 1000 km/hr. And they have accomplished this
in unprecedented detail.
Data received from the U of C-designed instrument sent to space on
a NASA launch from Alaska about two years ago was able to help
pinpoint the so-called edge of space: the boundary between the
Earth's atmosphere and outer space.
With that data, U of C scientists confirmed that space begins 118
km above Earth and the results were published this week in the
Journal of Geophysical Research.
The instrument – called the Supra-Thermal Ion Imager – was carried
by the JOULE-II rocket on Jan. 19, 2007. It travelled to an
altitude of about 200 kilometers above sea level and collected data
for the five minutes it was moving through the "edge of
space."
The Canadian Space Agency invested $422,000 in the development of
the Supra-Thermal Ion Imager instrument on JOULE-II.
The ability to gather data in that area is significant because it's
very difficult to make measurements in this region, which is too
high for balloons and too low for satellites.
"It's only the second time that direct measurements of charged
particle flows have been made in this region, and the first time
all the ingredients – such as the upper atmospheric winds – have
been included," says David Knudsen, associate professor in the
Department of Physics and Astronomy at the University of
Calgary.
Knudsen and his former PhD student Laureline Sangalli are the lead
authors of the paper. Co-authors include: JOULE-II lead scientist
Miguel Larsen of Clemson University, Robert Pfaff and Douglas
Rowland of NASA Goddard Space Flight Center and T. Zhan of Conseco
Inc.
"When you drag a heavy object over a surface, the interface becomes
hot. In JOULE-II we were able to measure directly two regions being
dragged past each other, one being the ionosphere -- being driven
by flows in space -- and the other the earth's atmosphere," says
Knudsen, who also is the head of the Space Physics Division of the
Institute for Space Imaging Sciences (ISIS). The institute is a
research partnership between the University of Calgary and
University of Lethbridge.
The measurements confirmed what other scientists consider the
boundary or edge of space.
"The results have given us a closer look at space, which is a
benefit to pure research in space science," Knudsen says. "But it
also allows us to calculate energy flows into the Earth's
atmosphere that ultimately may be able to help us understand the
interaction between space and our environment. That could mean a
greater understanding of the link between sunspots and the warming
and cooling of the Earth's climate as well as how space weather
impacts satellites, communications, navigation, and power
systems."
The U of C-designed instrument has been adopted by COM DEV, an
Ontario-based global designer and manufacturer of space hardware,
and is being used as a prototype for three instruments currently
being readied to fly on the European Space Agency's "Swarm"
satellite mission, set to launch late next year and to collect data
for four years. The JOULE-II instrument is one in a long list of
more than a dozen instruments designed by U of C scientists in the
past forty years which have flown in space. There are at least five
more being readied to go on missions in the next two years.
"Understanding the boundary between the Earth's atmosphere and
outer space is fundamental to the bigger picture of the effects of
space on the Earth's climate and environment," says Russ Taylor,
the director of ISIS and head of the Department of Physics and
Astronomy at the U of C. "This detection is part of a long history
of success by ISIS researchers in designing and building innovative
instruments flown on rockets and satellites to image the flow of
matter and energy between the Earth and Space."
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University of Calgary
Thanks to University of Calgary
for this article.