Statistics about auroras

Finnish Meteorological Institute has operated auroral cameras at several stations in the Finnish Lapland since 1970's. From the basis of the long time series of the camera images the diurnal and seasonal variations in the statistical auroral occurrence rates can be resolved. Also the
latitudes of maximun auroral occurrence can be defined.

Figure 1:
The monthly number of auroral nights. The red line shows that from South-Finland to Polar Circle there are two maxima within a year: in September/October and in March. During the Christmas time the occurrence of auroras is not so frequent. In North-Finland, north of the Arctic Circle, the best season for seeing auroras in December - January. During the summer, the nights are too bright for observing auroras.

Figure 2: The statistical hourly occurrence frequence of auroras in Lapland. Statistically, the best time for seeing auroras is just before the midnight. The occurrence probability is then about 80 % providing that the sky is not too much covered by clouds.

Figure 3:
The number of auroral nights in percentage of all nights in Europe. In Tromsö, Norway, at the coast of the Arctic Sea, almost all nights (during the dark seasons) are illuminated by auroras. The number of auroral nights decreases when moving southwards. In Oulu, in Finland at the latitude 65°N, the percentage is about 30, in Helsinki at latitude 60°N, the number is 5. In Central Europe the mean number of auroral nights is about one.