There’s been a flurry of activity on the sun over the past few days, which means we may get a chance to see a good display of the northern lights tonight.
On Wednesday, the sun belched a wave of charged particles that, if they reach Earth and interact with our magnetic field, can put on a spectacular light show.
Our sun goes through an 11-year cycle where activity waxes and wanes. Currently, we are in a period of heightened activity where the sun produces more sunspots, relatively cooler areas on the sun’s surface.
But because the sun, which has an incredibly powerful magnetic field, is not a solid mass and different parts rotate at different speeds, the magnetic fields around these sunspots can sometimes become entangled and then spontaneously erupt in a solar flare . These flares can disrupt radio transmissions here on Earth.
This image shows several sunspots on the sun’s surface on Friday. The numbers denote the groups followed by space-time scientists. (Spaceweather.com/NASA)
These solar flares are often followed by something called a coronal mass ejection (CME), where charged particles erupt rapidly and are carried by the solar wind.
If the Earth is in its path, the particles can disrupt our magnetic field, pushing it back until it sticks and the particles are sent poleward.
But not all CMEs produce large displays of aurora borealis, also called the aurora borealis.
For example, there is something called an auroral oval around the north and south poles. How far south the auroras can be seen depends on a few factors, including the speed and strength of the particles, as well as whether or not the oval is tilted south (for those in the north).
How and when
According to the US National Oceanic and Atmospheric Administration (NOAA). Space Weather Prediction Centerthere is a chance of a moderate geomagnetic storm Friday night.
This chart shows the geomagnetic forecast for July 22-24. (Chris Ratzlaff)
There is some debate as to whether or not we will get a storm strong enough to be seen at lower latitudes, say parts of southern Ontario and the northern United States.
Geomagnetic activity is measured by something called the Kp index. The higher the number, the more likely the aurora will be visible at lower latitudes. Some aurora watchers predict a Kp index of 8 or 9, which is quite high, while others believe it won’t be as powerful.
This is because the solar flare associated with the CME was moderate and not that powerful.
I agree. NASA & Predictions https://t.co/co9I52zA9Z
—@TamithaSkov
Either way, if the skies are clear tonight, you should still be on the lookout.
The best way to see them is to head to a dark sky spot with a decent view to the north. The sun doesn’t set until late in the evening, so you may have to wait until it’s quite dark.
To be able to see them from a light-polluted city like Toronto or Montreal, however, the Kp index will have to be quite strong, like a 9 or 10, which is not impossible.
Sometimes, if it is a weak storm, the auroras are not visible to the human eye. However, since cameras can leave shutters open for longer exposures, you might want to try setting up a camera on a tripod and taking a 10-20 second exposure set to ISO 800 to see if they are there, but it just isn’t visible to you.
For updates, there are many free apps like Northern Light Aurora Forecast and My Aurora Forecast & Alerts where you can keep an eye on the Kp index in real time.
You can also visit websites like Spaceweather.com and SpaceWeatherLive.
And if the forecast doesn’t pan out, don’t worry—the sun has just begun its peak phase, so there’s likely to be a few more years of solar activity and aurora viewing ahead.