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Beautiful sub-auroral arcs across the sky: what we know so far about the phenomenon

October 14, 2017

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Deeper into the glowing clouds

June 13, 2016

As I wrote my article yesterday, I was thinking June 11th was going to be the last night for noctilucent clouds in at least a week, and I had very little hope for June 12th. I actually thought of going to bed early las night, because stratus clouds were starting to show up from the south, veiling everything up! I went to bed, but I couldn't sleep. Typical...
11.30 - I looked out the window, just to make sure I wasn't missing out on anything. Surprise. I between stratus bands, one could distinguish some whiter bands. I'm taking my chances! I take my Sony camera out and my Sigma 150-500mm APO, and start shooting from my backyard some close-up shots, which, I wouldn't know how would turn out. 
 

And they turned out even better than expected! At 500mm, they develop kind of fast, but they display some beautiful smooth or rugged edges, troughs and mounts, whirlpool, twirls or waves. It is fascinating to see them moving this close and to think that they are made of so tiny ice particles. It's like they hardly obey the laws of physics up there in the mesosphere. The most stunning fact is when you realize that they are actually transparent, like plasma, because of the moving stars in the background of your time lapse.

Depending on how you look at it, this phenomenon reminds me of different things. First imagine you are at ski or on the snow. Well the top layers are always kind of blown away by the wind because they are small and thin snow flakes. When so, and if you are looking at them directly into the sunlight, they also make out the same wave and whirl patterns, only NLC are way smoother due to the thinness of its particles. Secondly it reminds me of the way some vapors or gases behave (ex: dry-ice flowing on a flat surface, or over-saturated alcohol vapors in a cloud chamber), that is if you can remember your physics class. But once again, it doesn't come close to that anyway. Way up there, the currents seem to be pretty active as the atmospheric pressure is be considerably low, and on the image above, it really forms a blizzard wave, or actually more like an ice-tsunami wave! 

 

 

There are structures and patterns that can easily recognized on the pictures but I am no expert in this field (for more info you are welcome to visit and read this really intersting website explaining and listing the different shapes: click here). However the easiest ones can be recognized: waves, lacunosus holes, net-like structures, large arcs, type S knots, whirls. You can take a closer look at them in the little gallery below.

 

In the meantime, I invite you to take a look at the little time-lapse I have made today. I had to watch it dozens of times, and I am still mesmerized every time I see the clouds moving. It's almost glamouring me, because it feels so light and delicate, yet powerful, like a glowing fantom wave descending on Earth. Supernatural? No, just beautiful physics and chemistry at play in the night sky!