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The Earth’s magnetic field is known to play a key role in causing the spectacular display. Some charged particles from solar winds get trapped in the Earth’s magnetic field, called the ‘magnetosphere’, which forms the auroral oval at the magnetic poles – the green circle on the picture to the left.
Land below the auroral oval, like Antarctica, Canada and much of Scandinavia, see the brightest lights. Pressure from solar winds can however squash the oval, like a balloon being pressed down at its neck, causing it to expand until the lights are seen as far away as the UK.
The brightness, colours and shapes seen depend on which atoms in the upper atmosphere the particles released from the magnetosphere interact with, and at what altitude.
The display occurs year round but is most visible when it’s darkest, around midnight and in the winter months.