"Solar activity is now trending upward with a maximum expected in early 2013."

ON ICY WINTER nights, the aurora borealis shimmers across the sky in an otherworldly light show.

These northern lights are seen best at the top of the world, from the far north of Alaska across northernmost Canada, Greenland, Iceland and Scandinavia, and into Russia.

Bundle up and take a northern-lights tour (offered from Fairbanks, Alaska, to Finland) or even a cruise (along Norway’s rugged coast). Or travel on your own to the north country from late autumn to early spring — preferably when the moon isn’t full — then hang around and hope for a good look.

Like the weather, the aurora borealis doesn’t pay heed to forecasts. Atmospheric conditions can keep everyone in the dark for days or nights. Or the sky could light up with dazzling green, sometimes rich-red, flashes or an hours-long eerie, dazzling glow.

Auroras are created when highly charged particles from the solar wind tumble into elements of Earth’s upper atmosphere. The science is complex; the result is simply dazzling.

During solar storms, the northern lights sometimes can be seen much farther south, even in the continental United States. And for night-sky watchers, the outlook is good, says NASA (the U.S. space agency), with more auroras on the way: “Following some recent years of deep quiet, the sun is waking up again. Solar activity is now trending upward with a maximum expected in early 2013. This means the greatest show on Earth … is about to get even better.”

Kristin R. Jackson is The Seattle Times’ NWTraveler editor. Contact her at kjackson@seattletimes.com.