And suddenly the night sky became red… blood red! Awesome picture by Ruslan Merzyakov in Svalbard, a Norwegian archipelago in the Arctic Ocean.
Ruslan Merzyakov explains:’Night till Monday was totally mind blowing. Never have I ever seen such red Aurora, but magical Svalbard made it happen.‘
The aurora is a natural light display that occurs in the polar regions. It is caused by charged particles from space catapulted down magnetic field lines into our upper atmosphere, where they collide with oxygen and nitrogen atoms to produce light. This process is driven by energy from the sun, which comes as a stream of charged particles called the solar wind that interacts with Earth’s magnetic field.
The aurora is most often seen as a green colour, perhaps rippling or twisting. To achieve a brilliant red or the fabled violets or crimsons, the aurora generally requires more energy and is much more rare.
The light from the aurora stretches up hundreds of kilometres in the atmosphere. Green light is produced lower in the atmosphere, at around 100 kilometres (62 miles), while red is seen higher, at 200–300 kilometres (124–186 miles). The next picture show clear curtains of light stretched out in a bright green that fades up into red, and then fades out altogether. The light is produced in rings around the poles, generally covering the latitude between about 65 and 75 degrees.
When there is more energy coming from the solar wind to drive the auroral processes, the aurora will be brighter and more colourful. Also, the rings around the poles expand and widen, so the northern lights can be seen at lower, more temperate latitudes. Very occasionally aurorae may even be seen in central Europe or the mid United States.
On these occasions, the aurora will likely be seen red in these lower latitude locations. Viewers will be looking north and seeing the top of the auroral curtain with the green lower part obscured by the surface of the Earth.
But on Svalbard, the Norwegian archipelago that sits in the Arctic Ocean east of Greenland between 74 and 81 degrees north, there is another reason for red aurorae: the “day-side aurora”. Day-side aurorae are only visible during polar night when it is dark at midday. They are less bright than night aurorae and usually red in colour, to which the eye is less sensitive than green, so it was only discovered in the 1960s that the aurora occurs during the daytime too.
Day-side aurorae are caused by charged particles from the solar wind that come in through the polar funnel of the Earth’s magnetic field directly into the atmosphere. They are not catapulted down field lines in the same way that particles are accelerated into the atmosphere on the night side, which is why the light display is not so bright.
So, did Ruslan Merzyakov witnessed a bright red aurora or a faint day-side aurora? Either way, the association with blood in the sky and the historical sense of foreboding make it a compelling opening for the Arctic thriller.