Earth's Auroras Make Rare Joint Appearance in a Feature Film

Scientists using NASA's Polar spacecraft have captured the first-ever movie of auroras dancing simultaneously around both of Earth's polar regions. During a space weather storm on October 22, Polar's Visible Imaging System observed the aurora borealis and aurora australis (northern and southern lights) expanding and brightening in parallel at opposite ends of the world. The images confirm the three-century old theory that auroras in the northern and southern hemispheres are nearly mirror images -- conjugates - of each other.

"This is the first time that we have seen both auroral ovals simultaneously with such clarity," says Dr. Nicola Fox, the science operations manager for the Polar spacecraft, based at Goddard. "With these images, we have the ability to see the dynamics of conjugate auroras."

Auroras occur when fast-moving particles trapped in Earth's magnetic field come crashing down into the gases of Earth's upper atmosphere. Those particles (electrons and protons) can only move along the invisible magnetic field lines, which are connected to Earth near the North and South poles. When a space weather event pours energy into the space around Earth and energizes the magnetic field, those particles travel to both ends of the field lines, creating auroral displays in approximately 2500 mile diameter rings encircling each pole.

"For the first time, the northern and southern auroral ovals were observed simultaneously with enough resolution to confirm that the northern and southern aurora are mirror images of each other on a global scale," says Dr. John Sigwarth, a space physicist at the University of Iowa who helped design and operate the VIS cameras. "Further analysis of these images should help us determine if the all of the auroral features are exactly mirrored down to the finest detail." Preliminary research suggests that while the auroras mimic each other on broad scales, there are also some fine features that do not match.

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