Northern Lights set to shine across Canada. Here's when
Wednesday, February 14, 2018, 7:03 PM - Check your weather forecast, be sure to dress warm, and get outside to look up! The Northern Lights are expected to make an appearance, shining in the sky across Canada on Wednesday and Thursday night!
The Sun spat out a small solar flare early on Monday, February 12, after a fairly lengthy period of quiet time. It was a relatively weak flare, though, only a C-class, rather than one of the stronger M-class and X-class flares, which are more of a concern.
However, it was accompanied by an eruption of charged particles from the Sun, known as a Coronal Mass Ejection.
Spotting this coronal mass ejection, aka CME or 'solar storm', thanks to NASA's Solar Dynamics Observatory (SDO) and the NASA/ESA Solar and Heliospheric Observatory (SOHO), space weather forecasters noted that it was heading straight for Earth. As a result, they issued a G1 geomagnetic storm watch for Wednesday and Thursday.
The geomagnetic storm watch, issued by NOAA's Space Weather Prediction Center
When the CME reaches Earth, which is expected sometime on Thursday, it will likely spark displays of the Aurora Borealis across Canada.
The map above shows the typical southerly reach of the Aurora Borealis, based on the strength of the geomagnetic activity being measured - the "Planetary K-index" (Kp). Any Kp value from 1 to 4 denotes "substorm" activity, and auroras are generally constrained by the blue line on the map. Anything Kp = 5 and above is considered to be a geomagnetic storm. Kp = 5 is a G1 (minor) geomagnetic storm, Kp =6 is G2 (moderate), Kp = 7 is G3 (strong), Kp = 8 is G4 (severe) and Kp = 9+ is G5 (extreme). Also, the higher the Kp value, the more rare the geomagnetic storm.
So, if the CME arrives as expected, and generates a G1 geomagnetic storm, residents of Canada at or north of the green line on the map should be able to see the Northern Lights, depending on their sky conditions. Those in southern Ontario, southern Quebec and the Maritimes will most likely not see the auroras this time.
Check your local forecast to see if you will have clear skies!
Update (Feb 15, 12:00 pm) - The CME arrived, as expected, very early Thursday morning (EST), although its impacts were perhaps weaker than expected, as it did not deliver a G1 geomagnetic storm as it passed. Some brief elevated geomagnetic activity was registered, and NASA's Suomi NPP satellite managed to capture the brightened aurora over Canada as it passed over the west coast, last night.
What does all of this mean?
Space weather forecasters watch for geomagnetic storms because they can cause problems with GPS signals and radio communications due to the impacts on Earth's ionosphere. In extreme cases, they can even cause widespread blackouts, by inducing currents of electricity along power lines, which disrupt the normal flow of power. The exact impacts depend on the strength of the storm. A G1 storm, the weakest category, only rarely causes any problems with our technologies, and they present little to no health risk to us on the surface (those flying on high-latitude, trans-continental flights, at the time, could be exposed to the radiation equivalent of a chest x-ray, though). The most noticable, and most anticipated impact of these events is the brilliant displays of the Aurora Borealis that results from them!
What is a geomagnetic storm, though? Basically, it is a disturbance in the 'bubble' of magnetic force that surrounds Earth, which then causes a variety of effects in the atmosphere, including the auroras.
Normally, the magnetic field generated by our planet protects us from many of the harmful effects of the Sun and the solar wind. Given the fairly recent findings that Mars' lack of a planetary magnetic field allowed the Sun's solar wind to strip away much of its atmosphere, it's very likely that we owe our very existence to Earth's magnetic field!
Once in awhile, though, Earth's magnetic field can become disturbed for a short time, mainly due to two different space weather phenomena - the solar wind, and coronal mass ejections.
The solar wind is a constant stream of charged particles leaving the Sun, which is divided into different 'ribbons' of flow - some dense and slow, and some sparse and fast - which pinwheel in an alternating pattern around the solar system as the Sun rotates.
A coronal mass ejection, also known as a CME, is a large cloud of charged solar particles that erupts from the Sun, usually following a solar flare.
To see both of these phenomena in action, watch the NOAA Space Weather Prediction Center forecast animation below, which runs from Feb 10 to 17, 2018, below:
The animation shows two different circular coloured plots, which give us a view of the inner solar system from above. In the top plot, blues are regions where there are fewer solar particles, while brighter colours denote areas with more solar particles. In the bottom plot, the slowest flows shows up as blue, and brighter colours showing the regions of faster flow. As the animation runs, you will see the different ribbons of the solar wind as they swirl around the Sun (the yellow dot at the centre), and how they sweep past the green dot (Earth), and the blue and red dots (NASA's twin STEREO spacecraft). At around 4 seconds into the animation, a small blob emerges from the Sun, and becomes stretched out into an arc as it advances towards the edge. This is the coronal mass ejection, which reaches Earth's location
The cone-shaped plots show the same information as the circular one, except from the "side", with Earth's north pole up, and the south pole down, so that we can see the space weather activity in three dimensions. The graph to the right of these plots shows how the space environment directly around Earth is impacted.
The impacts the solar wind and coronal mass ejections have on Earth are caused when Earth's geomagnetic field interacts with the magnetic fields these phenomena carry with them, as they move through space.
If the magnetic field of the solar wind or CME happens to point in the same direction as Earth's geomagnetic field, the two fields repel each other, the same way two magnets will repel each other, if you push the same poles (N-N or S-S) towards each other. This causes the solar particles to mostly divert around Earth's field, although the abundant particles in a CME can cause the sunward side of Earth's field to become compressed enough that there will be some elevated geomagnetic activity on the day side of the planet.
The more 'opposite' the magnetic fields are, the more strongly the fields will interact and actually connect with one another. In both cases - with the solar wind or a CME - when the magnetic field lines connect, charged solar particles flow from the solar wind or the CME into Earth's magnetic field. There, they become trapped, and then stream down into the upper atmosphere near the north and south poles.
When these charged, high-energy particles (mostly electrons and protons) enter the upper atmosphere, their electric and magnetic fields cause disruptions in Earth's ionosphere, which impacts radio signals. The particles also bump into air molecules, transfering some of their energy to them, and these molecules then dump that excess energy in as quickly and efficiently a way as they can, by producing a tiny burst of coloured light. The exact colour depends on what molecule - oxygen or nitrogen - is dumping that energy, and exactly how much energy they absorbed (which usually depends on how far they electron or proton had to penetrate into the atmosphere before hitting them). The result is the swirling, dancing ribbons of light that we call the Aurora Borealis and Aurora Australis, or the Northern and Southern Lights.
The exact intensity of geomagnetic activity sparked by the solar wind or a CME depends on three basic factors - density, energy and speed.
With one factor - a dense CME, or a high energy flow of the solar wind, or a fast transition between ribbons of the solar wind - and you get the lowest levels of geomagnetic activity, resulting in the weakest geomagnetic storms.
Add two together - a fast transition to a high energy part of the solar wind, a dense, fast moving CME, or a dense CME that was blasted into space by a powerful solar flare - and the intensity of geomagnetic activity increases.
Beware the coronal mass ejection that combines all three - very dense, very fast moving and containing a lot of energy! The last time one of these swept past Earth, it touched off what is now known as the 1859 Carrington Event. This event began as an extreme X-class solar flare, which may be the strongest solar flare ever witnessed, and although astronomers at the time did not see the coronal mass ejection that was blasted out by it, its impacts here on Earth were severe. It produced bright auroras that were visible all the way into the southern United States, and caused induced currents along telegraph wires that set poles on fire and shocked operators. The currents were so persistent along the system that operators were capable of sending messages along the lines for days after, even though there was no power source hooked up to the system.
A study performed by Lloyds of London estimated that if such an event were to repeat now, it would damage most of the satellites and spacecraft we have in orbit, as well as overload most power grids, causing widespread blackouts. The damage to technology and infrastructure would cost the world trillions of dollars, and recovery from the event would likely take years.
So far, the timing of the most powerful flares and CMEs that we've witnessed over the years have spared us such a disaster, but we have come extremely close on a few occasions. In the summer of 2012, when many people were worrying about the supposed upcoming Mayan apocalypse, three moderate-sized CMEs blasted out in very quick successon, combining together in space to form into one very dense, very energetic, and very fast-moving cloud. We avoided disaster because they passed through the space 'ahead' of Earth in its orbit. If they had gone off just two weeks eariyer, however, the resulting CME would have scored a direct hit on Earth, very likely sparking an extreme geomagnetic storm that would have rivaled or even exceeded the impacts of the Carrington Event.
Fortunately, since we're aware of these issues, governments are coming up with strategies to protect our technology and power grids against space weather events.
Sources: NOAA SWPC | With files from The Weather Network