Hot Skies over a Cold Landscape

摘要

Frozen tundra in the interior of Alaska might seem a most unlikely destination for a winter vacation. Despite the unforgiving weather, science-minded travelers from around the world are drawn to Fairbanks to witness one of nature's most spectacular phenomena-the aurora borealis. Best described as dynamic displays of glowing arcs and curtains, auro-rae light up the dark sky with a full spectrum of visible light, most commonly greens or pinks. They form when charged particles ejected from the Sun's upper atmosphere excite gas molecules in Earth's ionosphere. The charged particles in the solar wind are deflected by Earth's magnetic field and gathered in the sky around the north and south poles.