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Auroras setting up to WOW across Canada Thursday night

The Weather Network logo The Weather Network 2017-05-18
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Keep your eyes on the northern skies on Thursday night, as they may be filled by an impressive display of the Northern Lights thanks to a speedy stream of particle from the Sun.

Space weather forecasters have issued a geomagnetic storm watch for Thursday night, anticipating a G2 (moderate) geomagnetic storm to start off the night, followed by G1 (minor) geomagnetic storm activity for the rest of the night and well into Friday as well.

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So, what's going on here?

Imagine, for a moment, that you could safely look past the glare of the Sun, to see what's going on near its 'surface', and furthermore that you were capable of seeing the lines of magnetism that sprout from the rolling, boiling plasmas that make up that surface. If you were to have done that today, as NASA's Solar Dynamics Observatory did, you'd have seen this:

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While much of the surface is covered in swirling plasma (the fuzzy blotchy parts), and looping magnetic fields (white/grey lines) that help to confine those swirling plasmas and charged solar particles to the surface, one region stands out - the large dark splotch on the left, conveniently outlined by the thick dashed line.

This region is known as a Coronal Hole, and it is a place where the magnetic field lines of the Sun have opened up, leaving a large gap for plasma and solar particles to escape. While the Sun is constantly emitting a stream of particles known as the solar wind, the wind flowing out of this coronal hole is significantly faster, and is producing what's known as a Coronal Hole High Speed Stream - a ribbon of diffuse but very speed particles that is swiftly overtaking Earth in its orbit.

© Provided by The Weather Network When that ribbon does catch up with us, on Thursday night, it is expected to have a few different impacts on our planet's magnetic field.

Simply due to the speed of these particles, they will all carry a lot of energy along with them, and there will be a buildup of these high energy particles right at the boundary between the slow-moving part of the solar wind we're in now, and this speedy part that's catching up to us. This is known as a Co-rotating Interaction Region (or CIR), and it alone can have a significant impact on our magnetic field, causing auroras to spring up in our northern night skies.

One other thing that these solar particles carry with them, due to the fact that they are moving charged particles, is the 'interplanetary magnetic field', and there are different 'sectors' of the solar wind that have an interplanetary magnetic field that points in a different direction. Some point in the same direction as Earth's magnetic field (and thus they repel each other), and we have fewer interactions and fewer aurora displays. Others point in the same direction as Earth's magnetic field, allowing the IMF and Earth's magnetic fields to directly interact with each other. When that happens, it makes Earth's magnetic field less effective at keeping the solar particles away from the planet.

© Provided by The Weather Network When Earth transitions from one of these sectors to another, it's known as a Solar Sector Boundary Crossing (SSBC).

NOAA space weather forecasters are anticipating Earth encountering both the concentrated high-energy particles of the co-rotating interaction region AND the solar sector boundary crossing sometime on Thursday, ahead of the arrival of this coronal hole high speed stream (CH HSS) on Thursday night.

As a result, they are expecting a G2 (moderate) geomagnetic storm to spark just as the CH HSS arrives, and they also expect conditions to remain active for almost all of Friday.



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