Coronal mass ejections from the Sun hurl highly-charged particles towards the Earth's atmosphere which collide with oxygen, nitrogen and other molecules, thus displacing electrons. When these electrons recombine with other loose atoms, light is emitted which produces impressive displays across the planet's two geomagnetic poles. To be more specific, the most common colour observed during such displays is green with tints of yellow and which have as basis the excitation of oxygen atoms. In contrast, when nitrogen atoms are excited, one observes various shades of blue and violet displays which are less sensitive to the human eye. Finally, excitation of nitrogen and oxygen, especially at lower altitudes, yields displays which are rich in reds (as indicated by the examples below). Of course, most auroras produce a wide range and combination of these "primary" colours and it is not unusual, for example, to observe streams of green and yellow flares during such a display.

Alaska is the best place in the northern hemisphere to observe these "dancing lights", for it represents the geomagnetic northern pole. When coronal mass ejections are really massive, aurorae can be observed as far south as mid-California and the Scandinavian countries. Countries in the Mediterranean are very far away from either of the two geomagnetic poles and, therefore, have a very low probability for the observation of this marvellous phenomenon.

Note: Athens, Greece may have a geographic latitude of 38° N but what is of actual significance is the fact that its geomagnetic latitude is 31° N. As a result, other locations may have a geographic location which is lower than Athens, they may be characterized at the same time with a higher geomagnetic latitude and, therefore, have a much greater probability of having an auroral display. For example, the southern-most tip of Florida (25° N, 80° W) is a full 13° further south than Athens and, yet, is characterized with a geomagnetic latitude of 36° N or 5° greater than that of Athens.