Capturing two different kinds of aurora (the red and green bands seen here) at the same time, new images have revealed that the mysterious red glow might be caused by electrons raining down through the atmosphere.
Amateur astronomers have captured a strange combination of red and green auroras on camera, and physicists — who had never seen such a thing before — have now used these images to learn what may trigger the more mysterious part of the lightshow. Photographer Alan Dyer was in his backyard in Strathmore, Canada, when he saw the lights dancing overhead and started filming.
It looks like a looks like a celestial watermelon. The rind, a rippling green aurora, is well understood: It appears when the solar wind energizes protons trapped within Earth’s magnetic field, which then rain down and knock electrons and atoms around.
The swath of fruity magenta is more mysterious: Though scientists have known about these “stable auroral red arcs” for decades, there’s no widely accepted proof of how they form. One popular theory is that part of Earth’s magnetic field can heat up the atmosphere and, like proton rain, jostle particles.
But until now, researchers had never seen both of these red and green auroras side by side, says Toshi Nishimura, a space physicist at Boston University. “This strange combination,” he says, “was something beyond our expectations.”
