Still a chance this weekend to see Auroras across Canada
Friday, March 31, 2017, 1:07 PM - A cool planet-moon conjunction isn't the only thing we can see in the night sky this week, as a stream of particles from the Sun is set to spark off spectacular auroras, and they could be visible all across Canada!
Watch out for the Northern Lights!
If you have clear skies, try to get outside and somewhere dark, as most of Canada STILL has a chance to see the Aurora Borealis.
As of today, Friday, March 31, NOAA's Space Weather Prediction Center (SWPC) noted G1 (minor) geomagnetic storm activity overnight and into the morning period, then diminishing to sub-storm levels of activity afterward.
SWPC aurora forecasts from March 27 to March 31, 2017. Note how that the times on the left are in UTC, and have been converted on the right. Credit: NOAA SWPC/S. Sutherland
In the NOAA forecasts above, notice how the forecast can actually increase the expected geomagnetic activity, as it advances from one day to the next. This is especially apparent from Tuesday to Wednesday, when the expected activity on Wednesday night changed from G1 (minor) to G2 moderate, and from Thursday to Friday, when the substorm activity expected on Thursday night and Friday morning ramped up into a G1 (minor) geomagnetic storm for several hours.
So, even though there is only sub-storm activity forecast for the coming weekend, there is still the potential for some isolate periods of stronger activity at times. Thus, keep an eye out here for updates on what's expected!
The scale used in the forecast, which denotes the planetary K-index (an estimate of how much Earth's magnetic field will be disturbed by solar particles), corresponds to the map below, to give an idea of how far south auroras may be visible.
Exactly how bright and strong the auroras show up will depend on how far south they extend, and what the local viewing conditions are.
Getting as far away from light pollution as possible is a must. For most Canadians, simply driving outside of your city or town is good enough. For those living in the Windsor-Quebec City corridor, however, it may require a bit of a trip north.
Also, give your eyes at least half an hour to adjust to the dark, and look to the north.
In all likelihood, the aurora will be faint, and best captured via a digital camera taking long-exposure images. The green hues of light, given off by excited oxygen molecules, can stand out noticeably and possibly reds at the lowest levels. Other colours are usually more difficult to see with the unaided eye.
Here's what some people have been seeing this week:
What's causing this?
Early last week, a large crack in the Sun's atmosphere began rotating into view from here on Earth.
The view of the Sun from NASA's Solar Dynamics Observatory, showing extreme ultraviolet light (193 Angstroms), on March 27, 2017. The large coronal hole is highlighted with the dashed line. The thin white lines denote the shape of the local solar magnetic field, with looping field lines nearly everywhere except those extending from the coronal hole. Credit: NASA SDO/S. Sutherland
This feature - formally known as a Coronal Hole - has advanced across the Sun in the time since, dragging with it a stream of fast-moving solar particles, that is sweeping past Earth's position in space.
As of Monday, Earth was passing from a thin ribbon of the solar wind, which was packed with slow-moving, (relatively) low energy particles, into what is known as a Co-rotating Interaction Region (CIR). Located just behind the ribbon of slower moving particles, the CIR is where fast-moving particles from the coronal hole pile up on each other, as they get trapped by that ribbon, and the magnetic field strength from these particles increases. This caused the initial pulse of auroras on Sunday night and Monday morning.
Now that the CIR has passed, and Earth is in the Coronal Hole High Speed Stream (CH HSS), the auroras are persisting, but at a lower strength.
NOAA SWPC's WSA-Enlil solar wind forecast from March 27-March-30, 2017. Animation and labels by S. Sutherland.
While the thin ribbon is packed with particles, the overall magnetic field produced by them is roughly in the same direction as the magnetic field here on Earth. Thus, they just divert around the planet (as similarly-oriented magnetic fields repel each other). The wide expanse of the coronal hole high speed stream (CH HSS), however, has a magnetic field that's opposite to Earth's magnetic field. Thus, the particles can have a much stronger impact on Earth's near-space environment.
NOAA SWPC forecasts only extend out a few days, however this coronal hole high speed stream is expected to be sweeping past us until early next week, at least. Thus, this event could extend until next Tuesday or Wednesday night.
The Moon and two planets form a triangle in the sky
In the evening hours of March 29, just after the Sun has completely set, watch the western horizon as the stars begin to come out for a beautiful trio of night sky objects.
In addition to a very thin crescent Moon, two brighter objects will emerge from the glare of the Sun - the planets Mars and Mercury - to form a triangle with the Moon.
The March 29 conjunction. Credit: Stellarium/S. Sutherland
Mercury, which will be very near its maximum elongation (its farthest distance from the Sun, from our perspective here on Earth), will likely appear as the brightest, since it will be receiving (and thus reflecting) the greatest amount of sunlight of the three, and the Moon will be such a thin crescent at the time.
RELATED: Our view of the night sky depends greatly on local light pollution. What is Light Pollution and how does it affect Canadians?
Night Sky Forecast
Will the weather cooperate, to allow clear skies to view these events? Watch below to check out your cloud forecast for the week:
Viewing in southern Ontario may be good on Wednesday night, but with the storm coming in on Thursday/Friday, the skies will be completely clouded over.