What happened to that feckin' aurora then?!
So, no aurora then? What was that all about?
Sadly - as is all too often the case - the hype proved to be just that. Hundreds flocked to the Causeway Coast, ramming the car parks in the hope of ticking off that bucket list item. Eyes peering into the darkness, in vain they stared, the elusive green lights nowhere to be seen.
And now, after the disappointment, come the recriminations. The blame game. Even the slagging off of none other than our very own Barra Best, the cheek!
But what went wrong? Why the disappointment? In this blog, I want to offer a few reflections on Saturday night with the hope that those of you who were disappointed may be encouraged not to give up. And in the hope that you will see the aurora for yourself someday in the not too distant future.
1. There was not enough nuance in some of the forecasts
Some forecasts used words like ‘possible’ and ‘might’. Our good Northern Irish weather forecaster, Barra, was certainly one of those, being careful not to over-promise.
But too many others - whom I will not name here - avoided such nuance.
The fact is, aurora forecasts are not the same as weather forecasts. Although the science of space weather is advancing fast, it’s still a couple of decades behind Earth weather. We are still very much in the learning stage about space weather.
But, more than that, the nature of the forecast is different. When we see Barra on TV, he will be reporting on detailed weather modelling done by supercomputers with the Meteogroup. These forecasts - contrary to popular misconception - are now very reliable for the next 24-48 hours. When Barra says it’s going to happen, there’s a very good chance that it’s going to happen!
However, space weather forecasts are not quite like that. To simplify things down, I like to break my forecasting into three questions: (1) Is is possible? (2) Is it probable? (3) Is it here? The first two are relevant here.
(1) Is it possible?
What prompted the hype for last Saturday was that CME launched by the Sun last Wednesday. If the CME is pointed towards the Earth as it erupts, it will head towards us, normally taking around three days to arrive. That’s what led to the forecasts for the CME to hit us around lunchtime on Saturday. Based on the size of the Ejection, predictions are made as to the CME’s speed and magnitude. But these are estimates at this stage.
And once you’ve gone that far with the forecast, that’s pretty much as far as you can go. It’s then a waiting game. And, to coin a phrase, possible means possible. It means there’s a chance. But it certainly doesn’t guarantee things at all.
For me, it means: be ready. I was ready for Saturday night. And, as Saturday late afternoon/early evening approached, it was time for question 2.
(2) Is it probable?
As the CME approaches, it passes by the ACE satellite, about an hour’s journey time away from the Earth for the solar wind. ACE has all sorts of instruments that tell us what the solar wind is actually like. And then - and only then - can we really firm up what is likely to happen.
There are four things to look out for:
The speed of the solar wind - the faster the better
The density of the solar wind - the denser the better
The strength of the magnetism solar wind (called the Bt) - the stronger the better
And, most crucially of all, the magnetic orientation of the solar wind (called the Bz) - if it is negative, then it allows the solar wind better to couple with the magnetic field of our planet. And this allows the aurora to travel further equatorwards, towards the mid-latitudes.
That means that it’s only really in the few hours before darkness on any particular night that we can begin to firm up whether or not an aurora is probable.
And what of Saturday night? The CME did not arrive at ACE. The stats remained flat, and no aurora was likely at all. And we knew this by late afternoon/early evening on Saturday.
So, in future, when looking at forecasts, look for those who will give you this degree of nuance. Sadly, many did not - including some (nameless) organisations that I would have expected to do better!
Actually, it turns out the CME did eventually arrive. Only nearly a day and a half late! Just before darkness on Sunday evening, ACE satellite showed a reaction. Was everyone out a day early? Should then have been there on Sunday night?
No, not at all. The stats were very poor:
The density did jump up a bit
But the speed only jumped up very slightly to around 300 km/s. Fast, but nowhere near fast enough (I’d like to have seen it closer to 500 km/s)
The Bt jumped up - but just slightly.
And, crucially, the Bz remained pretty much resolutely positive.
A case in point, if ever there was one. Yes, there was a CME launched on Wednesday. Yes, aurora was possible. But, when we got the data from ACE on the Sunday evening, it was clear that it wasn’t actually going to be probable at all! And it’s only when you get this information from ACE that you can make that call.
2. Clickbait images were used on many of the articles
The fact is that many of the websites that were promoting the possible aurora were perhaps more interested in getting traffic to their sites than in accurate science reporting (either that, or they were genuinely ignorant of the science, and a severe case of Chinese whispers broke out on the internet).
I was seeing images of aurora displays from the Arctic Circle, the like of which are almost impossible here. So, even if the CME had turned up, people would not have seen anything close to what the images promised.
I even put out a tongue in cheek tweet about this very issue
Tempting as it might be to put amazing images out to attract clicks, if we’re going to raise people’s expectations, we need to do so in a realistic way.
3. There was not enough clarity as to what the aurora would actually look like
This follows on from point 2. We don’t live in the Arctic Circle. The aurora displays here are usually very modest. The camera, of course, sees differently than our eyes. Its sensor will pick up colour; at night, our eyes see with the rods and these do not pick up colour. If you leave your camera shutter open for 30 seconds, you will probably see colour. But, with your eyes, you will not.
Does that mean the camera is lying? No. It just sees differently. But it does mean that inexperienced people who go out need help in knowing what to look for. Most aurora displays in Northern Ireland look more like a faint enhancement along the northern horizon, a lighter grey band, colourless to the naked eye. That’s it. Especially in these times of solar minimum.
Now, I have seen some epic displays. I have seen the night sky shimmer and pulse with light. I have seen pillars dance before me. Most of the time, these had been colourless. But, on occasion, I have seen colour with my naked eye - or just about anyway.
But these are unusual. Don’t expect to see them as a matter of course.
What then do we learn?
Know the difference between when an aurora is possible and when it is probable - and you can only tell if it’s probable normally in the hours leading up to darkness.
Find online sources you can trust to give you this information.
Watch for clickbait images and don’t be taken in by them.
Know what to look out for when you’re out viewing. Turn off your car headlights. Let your eye get dark adjusted. And wait. Tenacity is a big, big part of aurora chasing.
I hope you weren’t too disappointed if you ventured out on Saturday night. I hope, at the very least, you had some good adventures, maybe with some good buddies, and got to enjoy the night sky in some magical location. Most of all, I hope you weren’t put off. Stick at it. When you see a decent display, you’ll be glad you did!