If you're still in the hunt for aurora borealis, the outbursts of hot, ionized gas the sun sent toward Earth on Sunday may just keep on giving.
Space-weather forecasters say that there's a 20 percent chance for a major geomagnetic storm tonight – an event stronger than last night's that would make any auroras visible farther south than last night's northern-light show reached.
To be sure, it's more likely that the storm will get no stronger than last night's, which turned out to be a bit more intense than forecasters had predicted.
Still, a 20 percent chance of rain sends many folks looking for an umbrella.
Even if tonight's conditions only match last night's, however, skywatchers in the right locations across northern Europe, as well as Canada and the northern US would get a second opportunity to grab some conversation-piece photos of a midnight horizon bathed in blue and green.
The current forecast
Data from sun-watching satellites suggest last night's event could have been more dramatic if Earth had been hit by the most dense part of the vast plasma cloud that raced by. Instead, the third rock from the sun encountered the plamsa cloud's suburbs.
Part of the uncertainty surrounding tonight's auroral activity stems from uncertainty about the distance separating the million-mile-wide mass of plasma that affected Earth yesterday and the one coming in behind it.
If Round 2 arrives Wednesday, either as a discreet event or attached to the tail end of yesterday's visitor, it will upset an already agitated magnetic environment around Earth, notes Douglas Biesecker, a physicist at the National Oceanic and Atmospheric Administration's Space Weather Prediction Center (SWPC) in Boulder, Colo. In that case, conditions would favor a geomagnetic storm at least as active as last night's, and perhaps more so.
If it comes in Thursday, Earth's magnetic sheath will have had extra time to settle down, reducing the effects of any disturbance that results.
These events are part of a larger solar awakening as the sun begins another sun-spot cycle – ups and downs in solar activity that peak on average every 11 years. So even if you miss tonight's activity because of bad weather, a desperate need for beauty sleep, or a wimped out geomagnetic storm, you'll have more opportunities as the cycle climbs toward its peak, currently projected for 2013.
Do-it-yourself aurora watching
If you are interested on keeping tabs on prospects for seeing an aurora somewhere other than where polar bears lurk, a good place to start is the aurora-forecast page run by the University of Alaska at Fairbanks's Geophysical Institute.
Aim your browser here. The map at the top caters to the home folks. But another map appears beneath it. In the upper lefthand corner, you'll find a "current view" box, where you can change the region the second map covers. The thin green lines surrounding the auroral ovals are the forecast team's best estimate of the southern boundary for viewing an aurora on a given night.
Even then, for people viewing the northern sky along that boundary with the naked eye, the aurora may appear as nothing more spectacular than a whitish glow on the horizon. Photographers at these locations capture images that show an aurora's true colors by taking exposures roughly 30 seconds long. You're value may vary, depending on how you configure the rest of your camera's settings.