You may get a chance to see the northern lights this week
The sun may be quiet, but that doesn't mean it's not doing anything. In fact, overnight Monday and into early Tuesday morning particles from it reached Earth, providing people with a beautiful northern lights show. The good news is you may get another chance to see it in the days ahead.
According to NASA's Space Weather Prediction Center (SWPC), particles from the sun may enter Earth's magnetic field on May 15 and 16 UTC (UTC is not a time zone but a time standard used by astronomers). This corresponds to May 14 and 15 for North America.
The culprit is an area of magnetic activity in and around a sunspot, or a cooler area on the sun.
The sun goes through a cycle of activity every 11 years. Right now it's in its quiet phase, with few sunspots — if any — on a given day (over the past year the sun has mostly been blank, with no sunspots).
However, over the past two weeks, we've had a few creep up. And this is good: When the sun is active, we get a better chance of seeing some activity here on Earth.
The northern lights are caused by charged particles that travel along the solar wind and interact with different molecules in our atmosphere. Every so often a sunspot can propel these particles much more quickly toward Earth. Usually, our magnetosphere acts as a shield around the planet, preventing most of the particles from getting in. But every so often, either there's an opening in the magnetic field or a lot of particles are moving quickly and essentially overpower it.
On Monday night an opening appeared in our magnetic field that allowed these particles to flow inward. It was a surprise display that thrilled many. They were even seen as far south as Iowa.
The Northern Lights are dancing over Prince Albert tonight. pic.twitter.com/gfXBv1ITe1—@OgrodnickDennis
If you missed it, good news: the SWPC is forecasting that three coronal mass ejections (CMEs) that released fast-moving particles are heading our way. Though they're not as powerful as some that are associated with solar flares, with any luck, our magnetic field will comply, and those charged particles will enter our magnetic field.
In northern Canada, in places like Yellowknife, Whitehorse or Fort Smith, the northern lights are seen frequently, as they travel along the magnetic field lines on the auroral oval, which is like a donut around the poles. Sometimes the donut shifts farther south, and that allows people farther south to be treated to the light show.
You could just go outside and look north (though, if you happen to be in the north, it could be south or all around you). Or you can check to see what your chances are of viewing the show in your area.
The SWPC has a scale called the K Index that measures geomagnetic activity on a scale from 0 to 10. For cities like Edmonton, Calgary and Winnipeg, a K index of 4 (or even lower sometimes) means you'll likely be able to see the northern lights. But for cities like Toronto and Vancouver, you'll need a higher index.
You can check the SWPC's site to find out where the measurement is on the scale. There are also apps available (search "space weather") and also sites like Spaceweather.com and Spaceweatherlive.com.
If you're in a city, try to get away from the lights. Drive a bit north and you increase your chances. Or you can set up a camera to take a 15-second exposure using an ISO of 1600 at f/4 or lower.
Remember that these are predictions based on observations, but there's no guarantee. Still, it's better to be prepared and not miss out on the potential of witnessing a truly magnificent sight.