In recent months the northern lights (aurora borealis) have been visible from all parts of the UK (Figure 1). This spectacular light show in the night sky is caused by activity on the Sun’s surface, emitting electrically charged particles that travel outwards.
Some of these particles are trapped in Earth’s magnetic field and travel towards the north and south poles, exciting atoms and molecules and causing them to emit electromagnetic radiation. The excitation of oxygen in the atmosphere gives rise to green colours, while nitrogen produces blues and purples. Very intense solar activity may result in red light from interactions of the solar particles with oxygen high in the atmosphere.
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