l The Northern Lights - aurora borealis - are caused by charged particles colliding in the Earth's atmosphere.
l They are seen above the magnetic poles of the northern and southern hemispheres.
l Green and pink are the most common colours, but there are also reds, blues, and yellows. The rare red aurora is caused by high-altitude oxygen, which can be as high as 200 miles above ground.
l Electrons and protons are hurled from the Sun's atmosphere, with some entering Earth's to collide with gas particles, causing the display.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
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Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
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