During a number of our expeditions we admire the dancing green lights of the Aurora Borealis or Northern Lights in the sky.  We admire them when we snorkel with Orcas in Norway or during our Ice diving trips at the White Sea in Russia. And though Heineken claims to play an important role in the green coloured skies, there is actually another theory behind this amazing phenomenon. We have collected a few frequently asked questions about the Aurora Borealis so next time you see the Northern lights, you might better understand it and enjoy the show even more !

What is Aurora?

Arctic circle Dive Center, White Sea, Karelia, northern Russia

White Sea Ice Diving expediton at the Arctic Circle Northern Russia, image by Franco Banfi

Aurora is a luminous glow of the upper atmosphere which is caused by energetic particles that enter the atmosphere.

What makes the colour?

The composition and density of the atmosphere and the altitude of the aurora determine the possible light emissions making different colour

What causes the aurora?

When energetic charged particles from the sun hits earth’s magnetosphere. The solar wind is the outermost atmosphere of our sun. The sun is so hot that it boils off its outer layers, and the result is a constant outward expanding very thin gas. This solar wind consists of protons and electrons. When these protons and electrons hit the earth’s magnetosphere, it causes aurora

How often is there aurora?

There is always some aurora at some place on the earth. When the solar wind is calm, the aurora might only be at high latitudes and might be faint, but there is still aurora. In order to see aurora, however, the sky must be dark and clear. Sunlight and clouds are the biggest obstacle to aurora observations.

Why does it have the shape of curtains?_DSA4638

The magnetic field confines the motion of auroral electrons. Think of it as pained magnetic field lines.

Where is the best place to see aurora?

And what time is the best? The best places are high northern latitudes during the winter, Alaska, Canada and Scandinavia. During very large auroral events, the aurora may be seen throughout the US and Europe, but these events are rare.

Can you hear the aurora?

This is a difficult question to answer. It is easy to say that the aurora makes no audible sound. The upper atmosphere is too thin to carry sound waves, and the aurora is so far away that it would take a sound wave 5 minutes to travel from an overhead aurora to the ground. But many people claim that they hear something at the same time when there is aurora in the sky. But one cannot dismiss the many claims of people hearing something, and this is often described as whistling, hissing, bristling, or swooshing. What it is that gives people the sensation of hearing sound during auroral displays is an unanswered question?

Arctic circle Dive Center, White Sea, Karelia, northern Russia

What is black aurora?

Sometimes you can have diffuse auroral curtains and arcs that have small gaps. These gaps are usually thinner that the arc thickness next to the gap and they look like a black aurora curtain embedded in the bright auroral glow around them

Can you predict when and where there will be aurora?

Yes, but with less confidence than weather prediction. The ultimate energy source for the aurora is the solar wind. When the solar wind is calm, we tend to have very little aurora, when the solar wind is very strong and perturbed, we have a chance of intense aurora.

Does the aurora have any effect on the environment?

Yes but it is limited to the high latitude atmosphere. Since the aurora takes place at about 90-100 km altitude, only the atmosphere at or above that height is affected by aurora. Some ionization may occur a few tens of kilometres further down, and can have effects on radio wave propagation.

Image taken in Norway during our Winter Whales of Norway expedition by Andreas Jaschek 2016

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