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Phenomenon: Northern Lights

The science behind the sky's natural fireworks display–and how to see it.

Dream of seeing the aurora borealis, but can’t afford a trip to the Arctic Circle? Try Minnesota’s Boundary Waters. The aurora is visible in the Lower 48 several times each year, usually in northern states during the spring. Dark and mild March and April nights are the best for viewing the display; that’s when the Earth’s seasonal tilt aligns the magnetic field to capture more of the solar radiation that creates the glow. Here’s how the sun lights up the night sky, and where you can see it.

(1) Violent storms on the sun’s surface (the corona) expel a high-velocity stream of charged subatomic particles known as solar wind. The frequency of these storms fluctuates according to 11-year solar cycles, which began intensifying this spring towards a predicted peak in 2011-12.

(2) When solar wind nears the Earth, the powerful (and potentially harmful) particles are deflected by our planet’s magnetic field–but not before the protective sheath absorbs some of their energy. As these gases move through the Earth’s magnetosphere, they are sucked towards the north and south poles like water down a drain.

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