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The aurora borealis - commonly called the Northern Lights - have put on a spectacular show the last couple of days.

Solar wind sparks amazing auroras in Canada, Round 2 tonight


Scott Sutherland
Meteorologist/Science Writer

Wednesday, May 13, 2015, 11:28 AM - A large coronal hole on the Sun sparked off a burst of auroral activity across Canada on Tuesday night and Wednesday morning, and the show may perform an encore tonight!

Who saw the best show?

There was still some uncertainty going into last night about exactly when the auroras would show up, and how far south they'd reach. However, apparently, the show was better than expected.

If you're living in northern regions of Atlantic Canada, Quebec or Ontario, and anywhere across the Prairies, northeastern British Columbia and northward from there, there was a very good chance you saw something last night, as shown below.


Aurora Forecast sample from 2:10 a.m. ET, May 13. Credit: NOAA Space Weather

These same regions of the country should keep an eye out for activity tonight, as the geomagnetic storm has a good chance of returning in the evening hours, and it could persist into the early morning.

As an example of what was in the sky on Tuesday night/Wednesday morning, and what may be visible tonight, here's a time-lapse from Stuart Milliner, in Balzac, Alberta, just north of Calgary:

Thanks Stuart!

What's going on to cause the show?

The Sun has been fairly quiet lately, with a few spits and spots worth mentioning, but amid that relative quiet, a strong wind has been blowing. A few days ago, a large coronal hole rotated into view on the face of the Sun. This region - the dark "open eye" of the winky face the Sun is making in the image above - is where the Sun's magnetic field lines have opened up, allowing charged solar particles to stream away from the surface at very high speed.

If we could view this from above the solar system, and see in velocity instead of light (thus not seeing the particles themselves, but how fast the particles are moving), it would look like this:


NOAA's WSA-Enlil Solar Wind Prediction graphic, from 21:00 UTC (5 p.m. ET) on May 12, 2015. Notations added by author.

The wide band of yellow-orange-red, with Earth's dot is right smack dab in the middle of it, is that fast stream of solar particles - a region of the solar wind called a "coronal hole high speed stream" (CH HSS). The reason why the particles of the solar wind are moving so quickly in this region is because they're traveling through space that has been 'swept clear' of other particles by a band of denser solar plasma that swept past us earlier in the week.

When those fast-moving solar particles interact with Earth's magnetic field, it can have the same effect as when a dense cloud of plasma (a coronal mass ejection, or CME) washes over us - it can cause a geomagnetic storm, resulting in a heightened auroral activity.

The CME shown in the image resulted from a large dark filament of solar material blasting away from the Sun's western limb. Since this solar plasma was launched out into space well ahead of Earth, it is not expected to affect us.

Share with us!

Did you happen to see the aurora on Tuesday night? Let us know in the comments below, or on Twitter (@ScottWx_TWN and @weathernetwork), and if you manage to take any pictures, please upload them into our galleries so that everyone can see!

Is that it? What if we missed it?

Fortunately, for anyone who wasn't able to get out to see this, or for whom the weather was uncooperative, NOAA space weather forecasters are expecting activity to continue all day today, and for the auroras to return to Canada early on Wednesday night. As with Tuesday night's forecast, the eastern half of Canada is favoured in the timing of the event, however the magnetosphere may surprise us once again!

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