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OUT OF THIS WORLD | Earth, Space And The Stuff In Between - a daily journey through weather, space and science with meteorologist/science writer Scott Sutherland

Auroras to shine across Canada due to speedy solar wind

Scott Sutherland
Meteorologist/Science Writer

Wednesday, September 28, 2016, 9:11 PM - A speedy stream of solar particles is washing past Earth this week, sparking off amazing displays of the Northern Lights in our night skies. Here's the best times and places to watch!

Keep an eye on the night sky this week, no matter where you are across Canada, because there's a very good chance you'll be able to see the Aurora Borealis, aka the Northern Lights.

The best nights to watch, based on the forecasts from NOAA's Space Weather Prediction Center, are Wednesday and Thursday. Space weather conditions are expected to reach at least G1 geomagnetic storm levels for both nights, with periods of G2 storm levels between sunset and midnight, EDT, and some potential for isolated G3 storm levels during those peaks. Adjust the timing according to your local time zone.

Typically, auroras from a G1 geomagnetic storm reach most regions of Canada, except the southern Atlantic provinces, southern Ontario and southern British Columbia. G2 storm levels produce auroras that stretch farther south, covering nearly all of Canada, and G3 even farther, giving all Canadians a chance to see this amazing phenomenon.

Geomagnetic storm watch, for Sept 28-30, 2016. Credit: NOAA SWPC

Light pollution will be your bane for spotting the aurora, as urban lights will completely wash out the delicate colours splashed across the horizon. If you want to check out the action, it's recommended that you get as far away from cities as possible. For most regions of Canada, this will be as easy as just heading north out of your community and keeping the city to your back when you watch.

Light pollution across Canada. Credit: Falchi et al., Sci. Adv., Jakob Grothe/NPS contractor, Matthew Price/CIRES

For anywhere in the Windsor to Quebec City corridor, however, the overlapping light pollution from multiple urban centres will be much harder to escape. There are pockets of darkness - along the shores of Lake Erie, Lake Huron and Georgian Bay, and between the larger urban centres - where you can escape this insidious glow.

Light pollution in southern Ontario. Credit: Falchi et al., Sci. Adv., Jakob Grothe/NPS contractor, Matthew Price/CIRES

Those in the Greater Toronto Area will need to head out of the city, though. Hop in the car and drive - either northwest to at least Orangeville or northeast towards Peterborough.

Give your eyes time to adjust to the dark. Between 30-40 minutes should be good, but the longer the better. Also, avoid any artificial sources of light - your phone, your car interior or exterior lights, streetlights, etc. The only lights that should be within your field of view, ideally, are the stars and the Moon. Fortunately, the waning crescent Moon should not present a problem to our viewing.

RELATED: What is Light Pollution and how does it affect Canadians?

Did you see it?

If you managed to spot the aurora, post your location and what you saw (colours, shapes, even noises) in the comments below!

What's going on here?

Often, when we hear about these brilliant auroral displays, they're due to what's known as a Coronal Mass Ejection, or CME. At some point, somewhere on the Earth-facing side of the Sun, a solar flare has gone off - an explosion of energy caused by the chaotic interaction of magnetic fields in the Sun's "surface" - and this has caused an eruption of solar material into space. This eruption is the CME. This cloud of material travels outward, and if it passes through Earth's position in space, a large number of charged particles in the cloud get diverted around us by the planet's magnetic field. Some of these particles get trapped by the magnetic field, however, and stream downward into the atmosphere, mainly near the north and south pole. When these particles hit the nitrogen and oxygen molecules in the atmosphere, they energize them, and in response, the molecules dump that extra energy as light. This produces bands and ribbons of colour in the sky, as the winds blow the energized molecules around.

In this case, there's been no specific solar flare and coronal mass ejection. In fact, the Sun has been fairly quiet as of late. What's going on now is that the Sun has developed a "Coronal Hole" - a region of the Sun's atmosphere where the magnetic field lines have opened up.

An extreme ultraviolet view of the Sun (193 Angstroms) from Sept 28, 2016, courtesy NASA's Solar Dynamics Observatory. Note the dark coronal hole that covers much of the northern hemisphere and a line across the Earth-facing side of the Sun. Modeled magnetic field lines, in white and grey, have been added for clarity. Credit: NASA

This shows up as dark regions on the Sun in various wavelengths of light, as shown above. Also shown in the image are the magnetic field lines that are extending out of the Sun's surface. In the lighter areas, the lines are looping out and back in. In the dark regions, the lines simply extend out into space. This is ramping up the normal stream of solar material that flows away from the Sun - the "solar wind" - to be much faster than usual, producing a "coronal hole high speed stream" or CH HSS.

Whereas there are far fewer solar particles in a CH HSS to interact with Earth's magnetic field, compared to during a coronal mass ejection, the speed of the particles more than makes up for the lack of numbers.

The result is auroras that can be just as far-reaching and vibrant as we'd see from any of the stronger solar eruptions that happen during times of greater solar activity.

Credit: NOAA | NASA

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