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New experiments that create a man-made aurora are helping researchers better understand how nitrogen in our atmosphere reacts when it is bombarded by the solar wind. Scientists from the Jet Propulsion Laboratory fired electrons of differing energies through a cloud of nitrogen gas to measure the ultraviolet light emitted by this collision, and the findings show our previous understanding of the processes that create the aurorae – which can also adversely affect orbiting satellites– may have been in error.



For more than 25 years, our understanding of terrestrial space weather has been partly based on incorrect assumptions about how nitrogen — the most abundant gas in our atmosphere –reacts when it collides with electrons produced by energetic ultraviolet sunlight and solar wind.

The new research has found that well-trusted measurements published in a 1985 journal paper by researchers Ajello and Shemansky contain a significant experimental error, putting decades of space weather findings dependent on this work on unstable ground.

New technology has allowed the researchers to better create and control the collisions and avoid the analytical pitfalls that plagued the 1985 findings.

The new results from the team at JPL suggest that the intensity of a broad band of ultraviolet light emitted from the collision changes significantly less with bombarding electron energies than previously thought.

The researchers studied ultraviolet light within the so called ‘Lyman-Birge-Hopfield’ (LBH) band to better understand the physical and chemical processes occurring in our upper atmosphere and in near-Earth space.

“Our measurement of LBH energy-dependence differs significantly from widely accepted results published 25 years ago,” said Dr. Charles Patrick Malone from JPL. “Aeronomers can now turn the experiment around and apply it to atmospheric studies and determine what kind of collisions produce the observed light.”

In addition to helping researchers to better understand space weather, which can help protecting the ever-growing population of satellites in Earth orbit, the new findings will also help further our understanding of phenomena like Aurora Borealis (the Northern Lights) and similarly the Aurora Australis (Southern Lights), which are caused by collisional processes involving solar wind particles exciting terrestrial oxygen and nitrogen particles at the North and South Pole.

The researchers are hopeful that their findings will also assist the Cassini project understand happenings on Saturn’s largest moon, Titan, as LBH emissions have been detected by the orbiting robotic spacecraft.

The research was published in IOP Publishing’s Journal of Physics B: Atomic, Molecular and Optical Physics.