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Climate & Space Prof. Ridley comments on new aurorae research in Scientific American

Why Do the Northern and Southern Lights Differ? Scientists have discovered the reason why. | Short Read

Climate & Space Prof. Aaron Ridley recently commented in a Scientific American article that examines the differences in the Northern (aurora borealis) and Southern (aurora australis) Lights. For decades, scientists thought when the phenomenon occurred in both pole regions simultaneously, the shimmer of the aurorae patterns mirrored each other. This was shown not to be the case in 2009. Now a team of researchers from Norway, Germany and the U.S. has discovered the reason why.

From the article:

“When the magnetic field lines curve symmetrically around Earth, aurorae should appear in identical places in the Northern and Southern hemispheres. And, if you could view both light displays simultaneously, they would look pretty much the same. But such a scenario is actually “quite rare,” says Aaron Ridley, a magnetosphere researcher at the University of Michigan…

“That’s because the sun also has a powerful magnetic field. It alters the path traced by Earth’s field lines, squashing the lines on our planet’s dayside facing the sun and elongating the lines on the nightside, creating a magnetic tail. As a result, Earth’s magnetic field appears to trace the outline of a housefly—the insect’s rounded head looking toward the sun and its elongated body and tail pointing away.”

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The electrons absorb laser light and set up “momentum combs” (the hills) spanning the energy valleys within the material (the red line). When the electrons have an energy allowed by the quantum mechanical structure of the material—and also touch the edge of the valley—they emit light. This is why some teeth of the combs are bright and some are dark. By measuring the emitted light and precisely locating its source, the research mapped out the energy valleys in a 2D crystal of tungsten diselenide. Credit: Markus Borsch, Quantum Science Theory Lab, University of Michigan.

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