Mother's Day Aurora
Sometimes it’s those unexpected pleasures that are the best. Like bumping into an old friend in the street. Like when a favourite tune you haven’t heard in years comes onto the radio (or, more likely these days, onto the shuffle mode in your iPhone).
The aurora of Mother’s Day was one such experience for me. Of course, all of us who call ourselves aurora chasers were well aware that there was the possibility of some aurora action on 6 March. Three days previously, a coronal hole on the sun (an area on the sun’s surface with open magnetic field lines which allows very fast solar wind to escape off out into space) had rotated into a geoeffective position (or, in layman’s terms, it was pointing towards us). When this happens, the chances of aurora activity are always increased.
But no one seemed to be expecting it to be a major storm or anything quite like the event it turned out to be.
Earlier on the Sunday, I was keeping half an eye on the stats. It was Mother’s Day, after all, and I was out with my family spoiling rotten the very long-suffering Mrs H. In the skies above, a low, thin wash of cloud covered the sky. Even if we get any action tonight, I thought to myself, there is little chance of us seeing anything much if that remains. And so, we wiled away a very pleasant afternoon, enjoying a fine meal and some good family time. And I gave very little thought to anything aurora-related.
It was only when I got home in the early evening that my interest got piqued. For one, the skies had indeed cleared, and I considered heading out later once we’d got the night time routine finished. I checked the stats from the ACE satellite: the Bz had dropped south at around 14.00, to a pretty impressive -15 nT, and it seemed to be staying mostly southwards. And at around 18.30, the time I was looking at stats, the solar wind density had begun to fall, and the speed begun to rise. (This is an indication that the Coronal Hole High Speed Stream had arrived – as the HSS speeds towards us, it creates a kind of bow wave ahead of it, rather like the bow wave in a speeding boat. This causes the solar wind ahead of it to bunch up, producing an increased density. Then, as the HSS itself arrives, the density drops and the speed increases. And this is exactly what ACE data showed). It was definitely looking interesting. It wasn’t quite dark by this stage in Northern Ireland, but it was going to be worth keeping an eye on this one.
But the clincher was a post by James Rowley-Hill on Aurora UK on Facebook. From the deepest southerly depths of Norfolk, where it was already dark, he was already reporting green in the sky. I popped out for a quick test shot. I pointed the camera north and took a photo: to the west, the remains of twilight were still glowing along the low horizon; but to the east there was already green beginning to show. It wasn’t yet fully dark across the whole sky, and yet we were already game on!
I checked the magnetometers. They were twitching away rightly (these measure the magnetic disturbance in our atmosphere that an active aurora brings – the greater the amplitude of movement on the graphs, and the further south that happens, the better for us). This was going to be a good display!
There was no time to lose. From the stats and my observations, I knew that the aurora could go into more active display at any time. And, when that happens, the last thing you want is to be driving somewhere looking out the car window at spectacular pillars in the sky. So I headed straight for a river near my house, not wanting to miss anything.
Once in position, I took a panoramic picture of the aurora arc in the sky. There, to the west, was twilight; and, to the east, an increasingly prominent and elevated arc. It was clearly visible to the naked eye, albeit without any colour (at this stage, at least!). On camera, however, there was an intense green glow, sitting well above the horizon. The skies were almost totally clear now. Everything was in place for a great show.
I moved along a bit and got beside some trees for foreground interest and scale in the photo. A few more shots, and I was posting on my Facebook page that things were happening. I only tend to do this for shows that people have a chance of seeing with the naked eye. I felt good about this one – and it turns out that my confidence was very well placed.
The shots I posted on Facebook to let people know about the display. I posted one which showed what the camera saw. I also processed one to show people what they could expect to see with the naked eye if they headed out. I think it's important to help manage people's expectations of what they will see if they go out without a camera.
The arc intensified in colour. And then, suddenly, just before 20.00 the most amazing display sparkled into life before my very eyes. At first, the rays shot upwards, purple pillars of light, stretching far into the sky above. As I’d only popped out for a test shot earlier, I only had my 18-55mm lens with my – the display quickly filled the field of view that lens offered and spilled out further, unconstrained by any limits my lens sought to place on it, a free spirit that was determined to put on quite the show.
Within no more than ten minutes, this free spirited aurora had broken free even of the constraints of these pillars, as it seemed to launch dollops of aurora colour free into the sky. (Little did I know at this stage that a later part of the display would do this with even more spectacular results).
If you look at the magnetometers for 20.00, you can see the flicker that corresponded with this brief but intense active period. This is why the magnetometers are such a good way of monitoring activity in real time. When out aurora chasing, you should pay careful attention to these and track them carefully.
And then, things settled down a bit. Aurora shows tend to come in periods of activity, followed by quieter periods, before activity may return again. So, I took my chances and headed back to the house. I wanted my 12mm Samyang lens and another memory card.
Ten minutes later, and I was back, this time with my ultra-wide lens, and ready for whatever this free spirited aurora had in store for me.
And it didn’t take long for it all to spark into life again. But 20.40, there was already another distinct pillar thrusting up proudly from the western end of the arc. I took a few shots by the river, before heading back to the trees, keeping an eye on the sky carefully all the time.
The ACE satellite data shows that the Bz was remaining pretty much consistently south, again at a very respectable value of between -10 to -20 nT, and the solar wind speed continued to rise to over 500 km/s. But, this night, you didn’t need stats to tell you what was going on. All you needed was your two eyes. Because this beauty was about to launch into one of the brightest and most sustained aurora events I have witnessed so far.
The arc remained, elevated and undulating gently, and I snapped away and posted on social media. I was keen to let people know what was going on. For my many followers who have told me they would love to witness an aurora for themselves, I knew that this night’s show was going to offer amazing potential.
During this time, the Bz stayed mainly south at more than -10 nT; this aurora was charged with potential, and it was likely to spring into life at any point. I wasn’t going anywhere.
And of course, at around 21.30, it all kicked off again – and then some! This time, the pillars appeared first to the extreme east, before spreading all along the eastern side of the arc. High above, in the purple zone of the aurora, the pillars rose clear and free, so distinct to view with the naked eye, high and far up into the night’s sky. The green arc below began to writhe with activity. There were patches of very intense light that were not only visible to the naked eye, but visible in colour as intense blotches within the main arc. I set the camera on timer to take a few selfies with the display in front of me, glorying in the view that was painted all across the sky in front of me. Similarly to the earlier substorm, within about 10 minutes the structure began to dissipate, and the aurora lobbed off blobs of colour into the sky above. In this shot, you can see a band beginning to rise up from the main display – oh, and there’s a meteorite fireball tracing across the sky in front of me too. That got me very excited as I was standing there holding this pose, I can tell you!
This liberated blob rose further and further. I have seen these aurora blobs before, most notably in the St Patrick’s Day aurora of 2015, when the lights through off many of these blobs all across the sky, causing it to throb, writhe and shimmer with life. This time, it was a bit more of a minimal affair. As I watched, it arced slowly above my head, high up in the sky. It tracked right above me, and then headed off to the north west. As it travelled, it was accompanied by some red rays; they themselves seemed to head up towards a perspective point, if not quite above my head, then not too far off it. It wasn’t a corona by any stretch of the imagination, but to have the aurora appearing nearly overhead in Northern Ireland is still a pretty cool happening. Not long before it disappeared, the green blob split in two, forming a giant auroral exclamation mark it the skies above. Given the scale of the show, it seemed entirely fitting that the lights should make some use of some excited punctuation; but the day it forms a winky face emoji, now that would something really special.
Again, when we look at the magnetometers, we see how this active period corresponds with some very clear fluctuations, and even quite far down to the south. Once more, if you want to get the heads up when the aurora might be about to kick off into a more visible show, keep your eye on these graphs.
For the next 45 minutes or so, the aurora shimmered away self-contentedly to itself, with various short bouts of rays being thrown skywards as it seemed to enjoy frolicking across the sky. Within the broader green arc, more intense "sub-arcs" wove and danced around, just above the horizon (the magnetometers continued to undulate during this period, as the graph shows). By 23.00 hours, it had settle back down into the green arc, low on the horizon. Although there was the chance for more activity that night (and indeed it did pick up again in the wee small hours), I had to get up early the next morning, so I called it a night, my 2016 aurora chasing hunger sated by the feast over the past few hours. My tripod was freezing cold; a slight frost had developed on it in the crisp conditions. My hands were a bit on the numb side. But I didn’t care. I had just had the most delightful of unexpected encounters with my old sky dancing friend.