The Aurora Borealis

What is the Aurora Borealis Made out of:

The Aurora Borealis is caused when the solar wind ions collide with nitrogen and oxygen atoms from the Earth’s atmosphere. The solar wind- which is when ions continuously stream from the sun's surface- makes the auroras more active. Magnetic storms-interaction between charged particles from the solar wind and the Earth’s atmosphere- can lead to, during the time around the spring and autumnal equinoxes-an autumn day when day and night are generally of equal length- be seen in the midlatitudes.

When was the Earliest Record of the Aurora Borealis:

The earliest record of the Aurora Borealis was in a 30,000-year-old cave painting in France. Some of the other earlier records that were seen were from astronomers. One of those astronomers was Babylon’s King Nebuchadnezzar 11 royal astronomer who inscribed his report of the Aurora Borealis on a tablet dating back to 567 B.C. There was also a Chinese report from 193 B.C which also notes the Aurora according to NASA.

Who Named the Aurora Borealis and Why?

Galileo Galilei-who was an Italian astronomer- named the Aurora Borealis (The Northern Lights) in 1619. He named it after Greek and Roman Mythology. Aurora being the Roman goddess of dawn and Boreas being the Greek god of the north wind. One of Galileo’s inspiring famous quotes was “You cannot teach a man anything, you can only help him find it within himself.”

What Colour is the Aurora Borealis and Why?

Most features of the Aurora are greenish-yellow Sometimes they will turn red at the tops and along the lower edges of tall rays but most features of the Aurora are greenish-yellow. On rare occasions, the top part will get hit by sunlight which will cause the auroral rays to create a faint blue colour. On infrequent occasions, (once every decade or so), the aurora can be a deep blood-red colour from top to bottom. In the lower area, there may also be pink hues. In addition to producing light, the aurora also produces heat. When the electrons which cause the Aurora return to the original energy levels, the atoms emit visible light of distinct wavelengths, to create the display of colours we see. Depending on the wavelength of light emitted, the colours will change.

Can you Predict When and Where the Aurora Borealis Will be?

The Northern lights are visible from late August to early April anytime during dark hours. In order to see them, you need a dark clear night. Solar flares on the sun or solar wind are also needed. The most common way to forecast the Northern Lights is to use the Kp-index which you can use both for short-term or long-term Aurora prediction. The KP-index is simply a scale that measures the geomagnetic activity directly related to the Northern Lights' visibility. The Northern Lights will be further south when the Kp-Index is higher. The higher the Kp-index the more likely you are to see a big Northern Lights display at high latitude.

Does the Aurora Borealis Have any Effect on the Environment?

Yes. Aurora Borealis causes mesospheric ozone layer depletion, which could have significance for global climate change. It is also limited to the high latitude atmosphere. Since the Aurora Borealis takes place at about 90-100km altitude, only the atmosphere above or at the height is affected. A few tens of kilometres further down, some ionization may occur and can have effects on radio wave propagation.

Is Wildlife Affected by The Aurora Borealis?

Sort of. During an auroral display, dogs will often look at the sky and bark suggesting that other animals are also aware of them. Although it isn’t certain it is well documented that there are things that animals are aware of that humans aren’t. Animals may be able to sense natural disturbances caused by an active aurora.

Can You Hear The Northern Lights?

There is no scientific evidence that you can hear The Northern Lights. The upper atmosphere cannot carry sound waves as it is too thin. It would take a sound wave 5 minutes to travel from an aurora to the ground as the Aurora is too far away. Many people claim to have heard something at the same time as the Northern Lights occur. This is often described as hissing, whistling, bristling or swooshing.

Does Moonlight Affect The Northern Lights?

It depends on how intense the display is. Moonlight affects visibility if the aurora is faint; bright moonlight will make it harder to see or not visible at all. However, if the Aurora is bright, you will be able to see it in full moonlight. The moon produces a much more blue-black sky as it illuminates the foreground.

Do Other Planets Have Auroras?

There are auroral emissions on Jupiter, Mars, Saturn, and, it is believed, Uranus and Neptune as well. On Jupiter and Saturn, the auroras produce emissions in ultraviolet and infrared which are not visible to the naked eye. Although, specialist cameras can capture them. There may be some visible ones as well, but they wouldn’t look anything like the ones on earth. Mars has an aurora but it is completely different to other planets as Mars does not have a global magnetic field. As an aurora is dependent on a planet's magnetic field the aurora on Mars does not appear as rings like we see on earth. The Mars aurora only occurs in certain places near magnetic rocks on the surface and it is much more localised. These Auroras have been seen from Voyagers 1 and 2 which were the first probes to bring back pictures of them. Since then, the Hubble telescope has also taken pictures of them.