Energetic particle precipitation (EPP) influencing the electricity production by wind power in Northern Europe

Earlier studies have shown that geomagnetic activity, used as a proxy for energetic particle precipitation (EPP), can influence the wintertime weather conditions, e.g. temperature and wind speed, on the surface of the Earth. This effect is transmitted via the polar vortex, the westerly wind system circulating the polar area during winter, which can intensify due to increased EPP activity. Stronger vortex tends to cause mild, wet and more windy winter weather in Northern Europe while weaker vortex leads to cold, dry and less windy winter weather. The EPP effect on the vortex is greatly dependent on the phase of the equatorial stratospheric zonal winds, called quasi-biennial oscillation (QBO), and is stronger during easterly QBO winds. Previously it has been shown that the EPP effect on the polar vortex influences the wintertime electricity consumption in Finland that is greatly dependent on the outdoor temperature.  Since the strength of the polar vortex also affects the wind speed on ground, we now study how energetic particle precipitation would influence the electricity production by wind power. In general, the electricity production by wind turbines is proportional to the wind speed. Here we find that during easterly QBO winds the geomagnetic aa index (proxy for EPP) correlates significantly with the wintertime wind speed in Finland and Sweden and also with the wintertime electricity production by wind power. This correlation can explain about 30-40% of the inter-annual variations of wintertime wind power production in these countries during QBO-E winters.