The level of magnetic disturbance varies over the day as Kiruna moves from the quiet daytime region under the zone of active aurora at night. The variation in magnetic activity is close to that of visible aurora.
The level of magnetic disturbance varies during the year, with slightly more disturbance on average around the equinoxes (23 March, day number 83 and 23 September, day number 266). The same variation is seen at other sites and in global averages. It is thought to be due to the changing angle between the Earth's magnetic dipole axis and the solar wind as the Earth moves round the sun in its orbit. The same seasonal variation is seen in visible aurora.
The level of magnetic disturbance at Kiruna is here compared with the 11-year variation of the Sun's activity. Magnetic activity seems to have increased slightly since the 1960s, as has the mean level of solar activity. However, there is no sign of any regular 11-year cycle in the local magnetic disturbance level in Kiruna.
statistics prepared by Sheila Kirkwood, 4 July 1997