This phenomenon occurs at a height of 100km and takes the form of a curtain fluttering in the wind, or points of light emitting from a single spot. A fascinating spectacle, caused by electrical impulses entering the atmosphere from the sun and being guided by magnetic fields. The Northern Lights appear all year round but can only be observed under a clear, dark night sky. In practice this means that they are most impressive in the autumn months, but they can also be seen in March and they ‘disappear’ in the light summer nights.