Amateur astronomers and aurora hunters have reported seeing a green glow in the skies over the UK. A phenomenon that can easily be confused with aurora borealis is called airglow.
This natural heavenly glow occurs all the time and across the globe. There are three types of it: day (dayglow), twilight (twilightglow) and night (nightglow). Each of them is the result of the interaction of sunlight with molecules in our atmosphere, but has its own special way of forming.
Daytime glow is formed when sunlight strikes the atmosphere during daytime. Some of it is absorbed by molecules in the atmosphere, giving them an excess of energy, which they then release as light, either at the same or at a slightly lower frequency (color). This light is much weaker than normal daylight, so we cannot see it with the naked eye.
The twilight glow is essentially the same as the daylight, but in this case, only the upper layers of the atmosphere are illuminated by the sun. The rest of her and observers on Earth are in darkness. Unlike daytime glow, twilightglow is visible to the naked eye.
Chemiluminescence
The night glow is generated not by sunlight falling on the night atmosphere, but by another process called chemiluminescence.
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Sunlight accumulates energy during the day in an atmosphere containing oxygen molecules. This extra energy causes the oxygen molecules to break down into individual atoms. This mainly occurs at an altitude of about 100 km. However, atomic oxygen is not able to easily get rid of this excess energy and as a result turns into a kind of "energy store" for several hours.
In the end, atomic oxygen manages to "recombine", again forming molecular oxygen. In doing so, he releases energy, again in the form of light. This produces several different colors, including night green light, which is not really very bright, but the brightest of all the glow in this category.
Light pollution and cloudiness can interfere with viewing. But if you're lucky, the night glow can be seen with the naked eye or captured in a photograph using a long exposure.
What is the difference between glow and aurora?
The green glow of the night sky is very similar to the famous green color that we see in the northern lights, which is not surprising since they are produced by the same oxygen molecules. However, these two phenomena are not related in any way.
Polar Lights
The aurora is formed when charged particles, such as electrons, “bombard” the Earth's atmosphere. These charged particles, which started from the Sun and accelerated in the Earth's magnetosphere, collide with atmospheric gases and transfer energy to them, forcing the gases to emit light.
In addition, the auroras are known to be arranged in a ring around the magnetic poles (auroral oval), while the nighttime glow is spread throughout the sky. The auroras are highly structured (due to the earth's magnetic field) and the glow is generally fairly uniform. The degree of aurora depends on the strength of the solar wind, and the glow of the atmosphere occurs constantly.
Auroral oval
But why then did British observers only see him the other day? The fact is that the brightness of the glow correlates with the level of ultraviolet (UV) light coming from the Sun, which changes over time. The intensity of the glow depends on the season.
To maximize your chances of detecting sky light, you should capture a dark and clear night sky with a slow shutter speed. The glow can be seen in any direction, free from light pollution, 10–20 degrees above the horizon.
