On Monday, NOAA’s Space Weather Prediction Center issued a G1 storm watch for increased geomagnetic activity on the 14th and 15th March. What does this mean exactly? It means that you could be in with a chance of spotting the Aurora from the north of the UK in the next few days!
What is a G1 storm?
The ‘G’ stands for geomagnetic, and the scale ranges from G1 all the way up to G5. This does mean a G1 is on the lower end of the scale, but there is still a certain threshold that needs to be met before you can even call it a storm.
A G1 storm corresponds to a Kp index of 5. Whilst Kp index is not the best measure of auroral activity, it can still give a general idea of where can expect the aurora to show up. For Kp 5, the aurora is approximately above the northernmost parts of Scotland. This doesn’t mean you can only see it there however; the aurora happens at altitudes upwards of about 100km, meaning you can see it even several hundred miles south of where it’s happening! The higher up you are as well, the further you can see. It’s for these reasons, we expect a storm of this magnitude could be visible in Scotland, northern England and Ireland. That might change however if it’s stronger (or weaker) than predicted.
What’s causing the storm?
Geomagnetic storm warnings can be triggered by many things. Usually, as is the case this time, they are caused by high speed streams of solar particles originating from the sun.
A coronal hole high speed stream (CH HSS) is the source of the fast solar wind we expect to be hit by in the next few days. Image: NOAA, NASA
The above image is from NASA’s SDO spacecraft, taken on Monday, and shows the outermost part of the Sun: the corona. The long, dark patch you can see is called a coronal hole and is responsible for the coronal hole high speed stream (CH HSS). As the name suggests, CH HSS is made up of solar wind which is much faster than usual. When the solar wind finally reaches Earth after a few days, its interaction with our magnetic field is notorious for creating increased chances to see the aurora at lower than normal latitudes.
How do I increase my aurora spotting chances?
As always, we recommend finding a spot with dark, clear, northward facing views that are free from light pollution. Coastlines and high up areas are good for this, as they also tend to let you see very far in the distance. For up to date alerts on the current status of aurora visibility in the UK, make sure to follow us on Facebook, Twitter, or download one of our smartphone apps.
What about “those” media reports of a giant storm?
Quite simply, they’re wrong. It looks like some reporters have misunderstood SWPC’s forecast. Perhaps thinking a G1 storm was the largest storm possible (when it’s actually the smallest).
