{"id":858,"date":"2017-05-10T12:50:47","date_gmt":"2017-05-10T12:50:47","guid":{"rendered":"http:\/\/wp.lancs.ac.uk\/aurorawatchuk\/?p=858"},"modified":"2017-06-22T13:21:49","modified_gmt":"2017-06-22T13:21:49","slug":"the-vivid-lights-what-causes-the-colour-of-the-aurora","status":"publish","type":"post","link":"http:\/\/wp.lancs.ac.uk\/aurorawatchuk\/2017\/05\/10\/the-vivid-lights-what-causes-the-colour-of-the-aurora\/","title":{"rendered":"The Vivid Lights: What Causes the Colour of the Aurora?"},"content":{"rendered":"

Traditionally, Earth\u2019s aurora are well known for appearing as a bright green glow across the night sky. Whilst green is the most common colour we see, it’s certainly not the only one! In this article, we talk about the different colours you might be able to catch if you see the aurora, as well as some of the science behind them.<\/p>\n

\"Aurora<\/a>

Green and purple aurora as seen from Scotland. Photo: ShinyPhotoScotland<\/a> via Flickr. CC BY-NC-ND 2.0<\/a><\/p><\/div>\n

It’s all in the\u00a0Atom<\/h1>\n

Auroral\u00a0origins lie in space, within what we call the solar wind. The solar wind is a continuous stream of charged particles which comes directly from the sun. The solar wind interacts with Earth\u2019s magnetic field<\/a>\u00a0and, eventually, results in charged particles entering our atmosphere close to the north and south poles. Here, these charged particles interact with gases in our atmosphere and cause the lights we see.<\/p>\n

The process of light emission happens right at the atomic level. Electrons can be thought of as orbiting around the centre of the atom (the nucleus) in what are known as energy shells. You can think of them as multiple ‘layers’, where higher energy electrons will\u00a0have a larger orbit.\u00a0When an electron in an atom comes into contact with a\u00a0charged particle originating from\u00a0the solar wind, it may ‘jump’ up to a higher excited energy level. But electrons always want to be in the lowest energy shell possible, meaning at some point it will drop back to its original energy.<\/p>\n

\"\"

A diagram of the emission of a photon from electron relaxation to a lower energy state.<\/p><\/div>\n

Where does this extra energy go? It gets released from the atom in the form of a photon<\/a> of light. The wavelength, and therefore the colour, of the photon depends on how much energy the electron gets rid of.\u00a0Different gases will\u00a0move electrons to different energy levels than others, meaning the wavelength and colour of the light emitted from them will also be different. This all occurs in a region at the top of the atmosphere about 100-600km high called the Ionosphere.<\/p>\n

Let’s take a closer look at some of these\u00a0and their associated colours:<\/p>\n

Green – Oxygen<\/h2>\n
\"2017_03_21_Aurora<\/a>

Green aurora as seen from Ballykelly, Northern Ireland. Photo: John Purvis<\/a> via Flickr. CC BY-NC-SA 2.0<\/a><\/p><\/div>\n

Starting with the most prominent of colours, the green aurora comes from the oxygen in our atmosphere. The oxygen green is emitted with a wavelength of 557.7nm (about 0.5 millionths of a metre) and occurs mostly around 100km altitude where the emissions last a very short amount of time (about 0.7 seconds).<\/p>\n

Red – Nitrogen & Oxygen<\/h2>\n
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#Aurora<\/a> #fishingboat<\/a> #light<\/a> #ness<\/a> #isleoflewis<\/a> #hebrides<\/a> 23:55gmt @VirtualAstro<\/a> @Wild_Scotland<\/a> @aurorawatchuk<\/a> @StormHour<\/a> pic.twitter.com\/HljQQlTva0<\/a><\/p>\n

— John-GM7PBB (@GM7PBB) March 30, 2017<\/a><\/p><\/blockquote>\n