Massive solar storm set to spark auroras across Canada this weekend

·5 min read
Massive solar storm set to spark auroras across Canada this weekend
Massive solar storm set to spark auroras across Canada this weekend

We may be in for a special Halloween treat Saturday and Sunday nights. Auroras may be dancing across our skies thanks to an immense solar storm the Sun blasted out into space.

On Thursday, October 28, NASA's Solar Dynamics Observatory was in the midst of its careful watch over the Sun. Of particular interest to space weather forecasters was a large, volatile sunspot cluster in the southern hemisphere, which they named Active Region 2887 (AR2887).

This cluster had been sparking and sputtering with minor and moderate flares for days. Around midday on Thursday, though, it suddenly blasted out an intense X1-class solar flare. The release of energy during the flare set off a 'solar tsunami' — a shockwave that spread out across nearly the entire face of the Sun.

Solar Tsunami 20211028 0171 - NASA SDO
Solar Tsunami 20211028 0171 - NASA SDO

The top panel of this composite image shows a closeup look at the southern hemisphere of the Sun and Active Region 2887, at the moment Thursday's X1 solar flare began. The three panels below track the solar tsunami that immediately radiated out across the Sun's surface over the next 30 minutes. Credit: NASA SDO/Scott Sutherland

Immediately following the flare, the top of Earth's atmosphere was bombarded by intense ultraviolet radiation and solar x-rays.

According to NOAA's Space Weather Prediction Center, this resulted in a strong radio blackout on the day side of Earth. Radio blackouts occur in the aftermath of strong solar flares, as the UV and x-rays from the flare disturb Earth's ionosphere, causing it to degrade or completely absorb high-frequency radio signals. This can completely disrupt radio communications between points on Earth's surface, and between the surface and satellite in orbit. A minor solar radiation storm has also been impacting Earth since the flare, due to solar protons being accelerated away from the flare region.

WATCH FOR THE NORTHERN LIGHTS!

Although the flare, the solar tsunami, and the radio blackout occurred roughly at the same time on Thursday, and the solar radiation storm began a short time after, there's one more impact from this event that we're still waiting for.

In the aftermath of the flare, an immense coronal mass ejection (CME) erupted into space, aimed more or less directly at Earth. A CME, sometimes called a 'solar storm', is a cloud of charged solar particles that can blast away from the Sun during a solar flare.

The initial CME eruption on Thursday was caught by SDO, but it was the NASA/ESA Solar and Heliospheric Observatory (SOHO) that captured its full scope.

SOHO has a special camera known as a coronagraph, which blocks out the direct light from the Sun using a small disk positioned in front of the camera lens. This allows the instrument to image the streamers of the solar wind. It can also capture coronal mass ejections as they erupt from the Sun's surface.

While it only takes around 8 minutes for the light and x-rays from a solar flare to reach us, and solar protons arrive tens of minutes after, it takes CMEs a bit longer to cover the distance between the Sun and Earth. Typically, they pass us a few days after the eruption. However, those from exceptionally strong flares can take as little as 16 hours to reach us.

Watch Below: Chris St Clair talks to TWN science writer Scott Sutherland about the Sun, CMEs, geomagnetic storms and the Northern Lights

Click here to view the video

NOAA space weather forecasters are predicting that this CME will arrive around midday on Saturday. It will likely spark a strong geomagnetic storm as it sweeps past and interacts with Earth's geomagnetic field.

NOAA SWPC ranks geomagnetic storms on a 5-point scale, from G1 (minor) through G5 (extreme). A G3 (strong) geomagnetic storm can cause some issues with power grids here on the ground and they have been known to cause problems with orbiting satellites as well. One of the best known and most highly anticipated impacts, though, are the auroras.

Auroras can be seen at pretty much any time of year in the far northern regions of Canada. However, during a geomagnetic storm, the arc the auroras follow pushes southward. The stronger the storm, the farther south the auroras can be seen.

Geomagnetic-Storm-Aurora-Extent-Canada
Geomagnetic-Storm-Aurora-Extent-Canada

For a G3 geomagnetic storm, the auroras stretch down across all of Canada. They may even be seen from parts of southern Ontario which are usually too far south to view these displays, although clouds and city light pollution will limit what can be seen.

The graphic below combines both the cloud forecast for the night of Saturday, October 30, and the expected extent of aurora visibility, based on the strength of the geomagnetic storm. Kp represents the "planetary K-index", a measure used by space weather scientists to track the strength of geomagnetic activity. The yellow Kp=7 curve shows the typical extent of aurora visibility during a strong geomagnetic storm.

Auroras Cloud and Visibility - Oct 30, 2021
Auroras Cloud and Visibility - Oct 30, 2021

Unfortunately, the sky forecast is not looking good for central and eastern regions of the country. There is the potential for auroral displays to persist into Sunday, though, so come back for updates throughout the weekend.

Thumbnail image provided by Alberta aurora chasers Tree and Dar Tanner.

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