When I was travelling back to Copenhagen (EKCH) from Aalborg (EKYT) I noticed something interesting behind the window – a halo-like rainbow around the shadow of the aircraft. I did not know exactly what it was back then – but I was sure it wasn’t just a lens flare. So I grabbed my phone and shot a short movie.
Later research firstly got me into the brocken spectre, but apart from the proper positioning I could not really see the magnified shadow of the aircraft (and the shadow was not distorted like it is often in case of the brocken spectre). It turned out that the halo-like rainbow around the shadow of the aircraft was the glory effect. The explanation of the effect is not something scientists can agree on. Currently it’s believed that the glory optical effect is connected to the classical wave tunneling. In other words – there are rays of light that pass from the air through the droplets (indeed – very small drops of liquid – and technically drops smaller than 500 micrometers in diameter). Some of the light is emitted backwards because of resonance effects. Of course, as the ray of light goes through different transmission media – the wavelength changes.
The effect manifests itself only when all elements are properly positioned: the observer is in between the sun and mist or fog (the sun –> observer –> mist/fog/clouds).
The glory effect is often seen with a brocken spectre – and that is the magnified shadow of the observer cast on clouds below the viewer. It’s a superstition, but “if one sees the brocken spectre in the mountains – that’s a good sign”.
What is very interesting is the fact that the glory/halo-effect is of the same size regardless of the size of the shadow cast on clouds (please see the composition picture).
The black lines match more or less the same ring colors – as you can see, the shadow of the aircraft has different size, yet the glory is practically unchanged.