ECE: Electrical & Computer Engineering
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Special Feature: SPACE WEATHER

Aeronomy of Ice

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The interaction between the solar wind and Earth's magnetic field and upper atmosphere can negatively impact the technology we rely on today &mdash and engineers and scientists at Virginia Tech want to do something about it.

Photovoltaic Clouds

Scott Bailey is interested in the interactions of space weather with the Earth's atmosphere. Why did noctilucent (night shining) clouds appear at about the same time as industrialization? Do the auroras play a part in ozone destruction? To get the data to study such questions, he has been active in building satellites, spacecraft, and equipment.

Why do noctilucent clouds form?

Photovoltaic Clouds

Bailey currently serves as deputy principal investigator of NASA's Aeronomy of Ice in the Mesosphere (AIM) mission, working with James Russell (BSEE '62), a professor at Hampton University. The AIM satellite is the first mission ever to study noctilucent clouds, which are called Polar Mesospheric Clouds (PMCs) when viewed from space. The clouds, when viewed from the ground, are seen as very bright clouds reflecting the sun at twilight.

"These clouds form about 50 miles high &ndash at the edge of space," Bailey explains. "The density of water molecules is one in a million. This is less than the Sahara desert, yet the clouds form &ndash always in summer and always in the polar region. What makes these clouds interesting is not just their striking beauty, but they did not appear until about 120 years ago. "Because their rise coincides with industrialization, there is a suggestion of a link."

Over time, the clouds have become brighter, have been seen more often, and appear to be occurring at lower latitudes. "We've never studied these clouds except as serendipitous satellite and ground observation. How do they form with so little water vapor? How does this work? We have a lot of theories. Once we understand how they form, we will be able to go back and determine if they have anything to do with global warming or human activity.

Do auroras take part in destroying the ozone layer?

Bailey is also involved with studying if and how the auroras impact Earth's protective ozone layer. "There is a large and growing body of evidence showing that solar energetic particles from the aurora lead to production of nitric oxide (NO)," he describes. "We know that there is an abundance of nitric oxide in the thermosphere (in the region of the auroras). When we get to polar winter, the night is so long, the nitric oxide may flow downwards. Then, when it comes down, it's a catalytic destroyer of ozone. It's not responsible for the ozone hole, but may have a part in the destruction of ozone.

These particles may form a coupling between the highest and lowest part of the atmosphere, according to Bailey. "The problem is, we can't measure nitric oxide at night. It's never been done." Bailey and Chris Hall, an aerospace professor, are working with researchers at the University of Colorado. The team has developed a method to look at how the atmosphere attenuates at night, and using that to calculate NO levels.

They are preparing a 5-minute sounding rocket flight in January 2010 from Poker Flat, Alaska. A large telescope payload (being built by Virginia Tech faculty and students) bolted to the rocket will focus on a bright UV star in occultation &ndash as it is being covered by Earth's atmosphere.

After the sounding rocket, the team hopes to expand the effort to include measurements on the same star, but from a satellite.

For more information, visit: www.space.vt.edu.