Naval Research: Airglow, Aurora, and Other Lights in the Sky

Image of HAARP

In the Copper River Valley, near a small town called Gakona in eastern Alaska, scientists are studying the airglow and aurora, and even creating their own. Although not as colorful as the natural aurora that often paint the skies over Alaska, the artificial airglow is proving very useful in understanding how the Sun's radiation affects the Earth's atmosphere and what that means for us.

Researchers at the High Frequency Active Auroral Research Program (HAARP) are using powerful radio antennae to study and even mimic what the Sun's energy does to the atmosphere. One reason understanding the atmosphere is important is to keep track of how it might change over time. We rely on the atmosphere for the air we breathe as well as protection from the Sun's powerful energy, so it's something we'd like to keep around. Different levels of the atmosphere are also very useful for communication, so studying them can help us communicate better.

Radio signals can be sent over great distances through the ionosphere, which starts about 35 miles (56 km) above the Earth's surface and extends up to about 500 miles (805 km). Storms on the Sun that send lots of energetic particles to the Earth and cause aurora can distort the ionosphere and interrupt our communications. Scientists at HAARP recreate, on a small scale, what happens when the atmosphere is excited by the Sun's energy.

Image of Elizabeth with telescope (courtesy Elizabeth Gerken)

Artificial airglow

When HAARP was used to excite a section of the ionosphere on several days in 2000, 2001, and 2002, researcher Elizabeth Gerken, a graduate student at Stanford University in California, was there. She and her fellow scientists watched the airglow created in the ionosphere through a telescope that has a special electronic camera called a charge-coupled device, or CCD. Red or green glass filters were placed in front of the camera's lens to allow it to "see" only certain types of light. The camera's shutter was kept open for 30 seconds so it could image faint glows that are invisible to the human eye. The camera sends digital pictures directly to a computer for processing into images that Elizabeth can then analyze. By studying how the ionosphere reacts to the experiments, scientists can begin to understand how it behaves during natural airglow and aurora.

 

Image of Sprite (courtesy Elizabeth Gerken)

Sprites and elves

Sprites and elves may sound like creatures you'd be looking for low to the ground, maybe near some fairies or leprechauns. But you'll need to look high in the sky to find the types of sprites and elves hunted by Elizabeth. Sprites are flashes of light that sometimes appear above thunderstorms at the same time lightning hits the ground or another cloud. Sprites are difficult to spot with the human eye because they are not very bright and because they last only a portion of a second. If you divide a second into 100 pieces, a sprite would be gone after just one or two! Sprites are also rare, only occuring with about one percent (that's 1 out of 100) lightning strikes. If you think you're fast enough to catch one, look under Resources for viewing tips. Pancake-shaped elves are even more fleeting than sprites, and appear slightly before them. Elizabeth and her fellow scientists use telescopes and television cameras to look for and record these phenomena (rare events). By studying the structures of sprites and elves, and the direction in which they develop, Elizabeth hopes to learn what causes them and to better understand the atmosphere.