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The northern lights (aurora borealis) are seen in the sky above Scugog in Durham region on Friday night.By Renata Valz Metroland
Here are 12 things to know about whether southern parts of Canada will get a Sunday night northern lights sequel as a “historic geomagnetic storm continues” — labelled such by the U.S.-based Space Weather Prediction Center.
We posed these questions to Robyn Fiori, a senior researcher and duty forecaster within the Canadian Hazards Information Service, who confirmed in a Sunday morning interview that on “Saturday morning, the sun did issue another large coronal mass ejection that we are expecting to arrive sometime today (Sunday), probably late afternoon or early evening.”
She answered these questions on how it will impact southern parts of Canada, in particular the northern lights.
1. What was the extent of northern lights visibility Saturday night into Sunday?RF: I don’t have reports as to how far south it was, which makes me think that maybe things didn’t spread quite as far Saturday night as they had the night before. Activity was starting to subside Saturday night.
2. What is happening with the sun right now?RF: The active region that has been causing all of the X-class flares and a lot of CMEs (coronal mass ejections) is starting to rotate off the Earth’s facing side of the sun, so we’re not going to expect as much activity from it.
But Saturday morning, the sun did issue a large coronal mass ejection that we are expecting to arrive sometime today (Sunday), probably late afternoon or early evening. We don’t think that we’re going to have as strong activity from this particular CME, but there is still going to be a possibility of seeing the aurora tonight.
Again, just like Friday night, you’re going to have to be in a clear location, not a lot of cloud cover, away from the city if you can.
3. Are we under a warning again right now?RF: The Canadian Hazards Information Service doesn’t have a storm warning issued, but we do have a geomagnetic storm watch issued until tomorrow (Monday) morning at 9 a.m.
4. So the previous warning ended?RF: The warning has ended. The main part of the warning ended yesterday (Saturday) afternoon just before 3 p.m. There was another brief period of warning last night (Saturday).
5. Is the storm watch issued because of the Saturday morning CME?RF: We’ve extended the storm watch until 9 a.m. Monday morning just to accommodate that CME arrival.
6. How long does it take for the CMEs to get from the sun to the Earth?RF: It’s entirely dependent on how fast it’s moving, but generally we’ll see them between one and three days after they erupt (from the sun).
7. Will it spark extended northern lights viewing into southern parts of Canada?RF: The CME that erupted (Saturday morning) has about the same characteristics as we saw in March of 2015. We call that our St. Patrick’s Day event. And that was an interesting event because you could see the aurora down to Ottawa, which does tell us there was some strong geometric activity. So there is certainly a chance tonight, but it’s probably not going to be as widespread as we saw on Friday night.
8. The geometric activity that caused Friday's spectacular auroras is no longer effecting us?RF: The geomagnetic activity that we saw from that large event on Friday night has subsided, yes.
9. So whatever happens tonight is from that Saturday morning CME?RF: Yes, any activity we see moving forward will be from the new event.
10: Sounds like southern Ontario might not get anything tonight; people will just have to go outside and look?RF: The big problem is we don’t know exactly how that cloud of plasma coming from the sun — that CME — is going to interact with the Earth’s magnetic field until it gets close enough for us to measure its magnetic field, and the magnetic field associated with that plasma cloud is going to have a certain level of interaction with Earth’s magnetic field. We can’t characterize that until we see it.
And that doesn’t happen until it arrives at what we call the L1 point. That’s about 30 minutes to an hour upstream of the Earth. So once we hit that L1 point then we have a better idea as to how big the interaction is going to be between the CME and the Earth’s geomagnetic field. But we really don’t have a lot of information before that.
11. Do you know when that arrival will be, can you measure how fast it’s coming and when we can expect it to arrive at Earth?RF: Yes, so when the CME erupted we get some estimates of the speed. The last estimate I saw was 900 kilometres per second, which is about twice as fast as the background plasma that is continually streaming off the sun. So we’re expecting it to arrive sometime in the late afternoon, early evening. But we can’t pinpoint an exact time.
But the fact that it’s coming later in the day and these kinds of a geomagnetic disturbances can last typically three to six hours, that’s pretty good timing to have a good chance of seeing the aurora overnight.
12. And this will be the last sequel from this so-called historic geomagnetic storm'?RF: The active region is still active but because the sun is rotating, any kind of eruptions that are erupting off of it aren’t going to be Earth facing any more. So we can still have a lot of activity from that active region but it’s going to be throwing off that ball of plasma and that radiation off to another region in space.
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https://www.toronto.com/news/geomagnetic-storm-watch-extended-until-monday-12-things-to-know-about-why-southern-parts-of/article_35c7e5ba-ec64-5f10-af31-a2c185fbaa9b.html
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