Southerly Aurora ~ Seen by Anders Jensen in Denmark on the evening of Sunday 22nd January.   Spectacular for its location so far south. Bright displays were also seen in England and other parts of Europe.  

"According to the auroral index something was going on and the skies were clear, so I put on warm clothes and went out on my bike just before 11 in the evening to find a dark spot in the countryside.

A test shot revealed a faint green glow in the northern horizon, and soon it became visible to the naked eye. After 15 minutes bright columns of light appeared, moving upwards and rapidly changing and blinking. And then a few minutes later a reddish glow could be seen above the green colours, with bright pillars dancing in between
.

©Anders Jensen, shown with permission

The sky glows with the green light of oxygen atoms, 90 – 150 km high, and excited by collision with high energy particles. The red is another atomic oxygen glow this time even higher. The glow below the green band is our own light pollution.

Contrary to popular explanations, aurorae are not caused by direct collisions between particles ejected by the sun and our upper atmosphere.

Solar particles are rarely energetic enough and if they could strike the atmosphere Earth would be a very different place with life as we know it probably non-existent.

Instead, we are shielded from solar bombardment. We have to thank currents deep in the earth’s white hot iron-nickel core (mostly molten but with a small solid centre) for that.

Its generated magnetic field extends well out into space and deflects incoming solar particles into a long magnetotail situated on Earth’s night side. There they are stored. Re-arrangements of the tail’s magnetic field can strongly accelerate some of the stored particles earthwards and it is these that light (fairly symmetrically) the northern and southern auroral ovals.


Atmospheric
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