Clouds glowing and flickering as if illuminated by flame. Noctalucence or other phenomenon?

On a recent holiday in the Yorkshire Moors, I observed clouds flickering red and yellow in a way in which I have never seen before. I captured the phenomenon on video, a link to which you’ll see below. The effect was as if the clouds were illuminated by a flame; the intensity and colour of the reflected light shifting rapidly as if caused by a flickering candle.

The observation occurred at 54°23'26.88"N 1°14'13.24"W on 23 June 2011. Observation began at 2210 UTC and the effect continued to beyond 2315 UTC (at which time I retired to bed, leaving my video camera trained on the sky in order to record any interesting developments). The phenomenon was observed at an arc of perhaps 30 degrees north-northeast. My compass suggested a range of between 020 to 040 degrees.

Initially, I wondered whether I was watching noctilucent clouds (which I do not believe I have seen previously) but a search on the Internet suggests that these are generally at extremely high altitude. I would guess that these clouds were no more than 5,000 ft (as a private pilot, I consider myself to be reasonably competent at estimating cloud height). They certainly weren’t at the tens of thousands of feet at which noctilucence typically occurs. And do noctilucent clouds shimmer as dramatically as these and in these colours?

My best guess is that it was simply sunset at altitude. The shimmering caused by the same process as causes light to bend in a mirage – photons complying with quantum electrodynamics – the “path of least time”; a gradation of air temperature (and hence density) causes rays of light to wiggle and seek the fastest path, opportunistically speeding through pockets of lower atmospheric density. Given that the light from the sun was travelling through tens of thousands of kilometres of turbulent atmosphere of constantly shifting density, perhaps this explains the flickering effect. Sun rays chaotically flaying around much as does a water hose when cast adrift. As the rays washed across the clouds, they flashed with illumination. But if this were the case, would you not expect it to occur commonly?

Or, perhaps my speculations are completely false and the explanation is quite different. Maybe it was simply a powerful light source over the hill, out of sight. A music festival? If you know better, please let me know. I’d be fascinated to know if you have specialised knowledge or experience which provides a more satisfying explanation. But please, rational explanations only – as entertaining as UFO etc. theories may be! Needless to say, it’s easy to imagine how our ancestors, lacking a basis of scientific knowledge and a rational mind, might easily resort to a supernatural explanation.

For completeness, here is how the landscape looks by daylight:

From Drop Box

And here's the video: