Abstract. This thesis focuses on the relation between geomagnetic activity and electricity consumption in Finland via northern annular mode (NAM). The NAM greatly affects winter weather in Finland and is also influenced by changes of the stratospheric polar vortex. Geomagnetic activity has been shown to have an influence on the polar vortex and thus also on the NAM and winter weather. It is shown here that during winter there exists a significant correlation between the NAM-index and the electricity consumption in Finland and this correlation is different in the two phases of the quasi-biennial oscillation (QBO), in other words, the direction of equatorial stratospheric winds, which are known to influence polar stratosphere and NAM.

In the analysis two different electricity consumption data sets were used: monthly data of total electricity consumption and yearly data of electricity consumption in households. These data sets are based on the electricity consumption data from Finland but also data from Norway and The United Kingdom were studied. The analysis included data from years 1980 to 2019. Since the monthly total electricity consumption data was only available from 1990 to 2019, it was necessary to reconstruct the missing values for the period of 1980–1989 by using monthly temperature data.

The relation between the aa-index and the total electricity consumption was also studied. In this thesis it is shown that there exists a good correlation of -0.64 between the aa-index and the total electricity consumption but only during negative QBO-phase. Some previous research concerning this topic have been made by using the NAO-index instead of the NAM-index. Thus also the NAO-index was used in this analysis and these results were compared to the previous ones.

The results indicate that there is a connection between the aa-index and winter’s electricity consumption in Finland via the NAM-index. This indicates that maybe in future it would be possible to predict winter’s electricity consumption by using the aa and NAM indices.