Space weather can be caused by giant solar flares and coronal mass ejections from the sun, and can adversely affect life on Earth. Tremendous blasts of radiation may threaten astronauts, disrupt satellite communication and navigation systems, and knock out power grids on Earth. Near Earth's magnetic equator, however, space weather can have dramatic effects even during quiet solar conditions.

"These storms are among the most explosive events that occur in the ionosphere, and are an important component of ongoing space weather research," said Jonathan Makela, a professor of electrical and computer engineering at Illinois.

"A better understanding of the physical processes responsible for these storms could improve our ability to forecast space weather," Makela said, "and lead to better techniques to mitigate its effects."

The ionosphere extends from approximately 100 kilometers to more than 1,000 kilometers above Earth's surface. In this region of the atmosphere, solar radiation can strip the outer electrons from atoms and molecules of gas. After sunset, the electrons recombine and give off light, called airglow. Space weather events at the magnetic equator appear as depletions in the airglow. As signals at radio wavelengths pass through these turbulent regions, they scintillate -- much like the twinkling of starlight at optical wavelengths.

Unlike aurora, which can be seen with the naked eye, airglow near the magnetic equator is visible only in photographs taken through narrow-band filters with exposure times of a minute or two.

In August 2006, Makela installed a narrow-field ionospheric airglow imager at Cerro Tololo Inter-American Observatory, located east of La Serena, Chile. The imager looks north, parallel to Earth's magnetic field and toward the magnetic equator. Two GPS scintillation monitors were also installed at the site, and are used to study ionospheric instabilities at a smaller size scale.

"The GPS monitors allow us to perform simple interferometric calculations and derive drift velocities of the perturbations that cause the scintillations," Makela said. "By measuring power fluctuations in the GPS signals, we can also correlate the scintillation patterns with the airglow images."

Makela is also attempting to correlate his airglow images with radar backscatter observations made with the Jicamarca radar system near Lima, Peru.

"In this way, we can study the relative roles of the equatorial and local regions of the ionosphere in the production of scintillation-causing perturbations," Makela said. "This could then help us better predict space weather, prepare further safeguards on Earth and in space, and plan more robust communication and navigation schemes during space weather events."

Makela will describe the instrumentation and present early results, based on overlapping data from the imager, GPS receivers and Jicamarca radar, at the American Geophysical Union meeting in San Francisco, Dec. 11-15.

Makela's work in Chile is in collaboration with electrical and computer engineering professors Paul Kintner at Cornell University and Brent Ledvina at the Virginia Polytechnic Institute and State University. Illinois graduate student Ethan Miller is also working on the project.

The National Science Foundation and the U.S. Naval Research Laboratory funded the research.

Note: If no author is given, the source is cited instead.

• Solar Flare
• Sun
• Northern Lights

• Geomagnetic Storms
• Weather
• Severe Weather

• Solar flare
• Geomagnetic storm
• Solar wind
• Van Allen radiation belt
• Magnetosphere
• Ionosphere