Why Are the Northern and Southern Lights Different?

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An aurora australis, the southern version of the phenomenon, as seen from the International Space Station in 2010.
Credit: NASA
▼ Auroraspaint the sky around the poles when the sun is particularly active, flinging highly charged particles at Earth's atmosphere. Scientists once thought that the gorgeous events were mirror images, but to their surprise, displays at the north (the aurora  borealis) and south (the aurora australis) don't precisely match.
Ever since scientists realized these two celestial displays don't line up, they've been trying to sort out why. Now, a team of researchers thinks it has found the reason — asymmetry in Earth's magnetic tail. But what's stranger is that the asymmetry is caused by the precise inverse of what scientists expected.
"The reason this is exciting is that earlier we have thought that the asymmetry in the system enters the magnetosphere by a mechanism called tail reconnection," Anders Ohma, a doctoral candidate at the University of Bergen in Norway and lead author on the new study, said in a statementreleased by the journal. "What this paper shows is that it's possible that it is actually the opposite."
It all comes down to Earth's magnetic tail, which is created by interactions between our planet and the sun. Those interactions begin with Earth's magnetic field, which scientists believe springs from the innards swirlingthrough Earth's core and creating an electrical charge. Magnetic fields — from refrigerators to planets — create invisible magnetic field lines arcing between the North and South Poles that can govern the behavior of material around them.
But Earth's magnetic fieldisn't the only one out there — the sun also has one, which affects the constant flow of highly charged plasma particles that streams out in every direction. The magnetic field embedded in that stream, called the solar wind, interferes with the one Earth produces, squishing it on the daylit side of Earth facing the sun and stretching it on the nightside facing away from the sun into a tail-like shape. (▪ ▪ ▪)

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