Effects of energetic electron precipitation on the northern wintertime atmosphere

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, lecture hall L10

Topic of the dissertation

Effects of energetic electron precipitation on the northern wintertime atmosphere

Doctoral candidate

Master of Science Antti Salminen

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Space physics and astronomy research unit

Subject of study

Space physics


Doctor V. Lynn Harvey, University of Colorado Boulder


Associate professor Timo Asikainen, University of Oulu

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Effects of electrons precipitating from the near-Earth space on the northern wintertime atmosphere

Varying amount of electrons precipitate from the near-Earth space into the Earth’s atmosphere all the time. This so-called energetic electron precipitation is driven by the particle flow from the Sun, the solar wind. Earlier studies have shown that electron precipitation directly affects, for example, ozone balance in the polar upper atmosphere. Moreover, several studies have shown that the effect of electron precipitation can extend to lower parts of the atmosphere, even down to the surface level.

This thesis work clarifies the effects of energetic electron precipitation and their mechanisms in the northern wintertime stratosphere. The thesis also examines how the effects of electron precipitation depend on the conditions of the atmosphere. The thesis is based on observational datasets of both atmospheric variables and electron precipitation, which are analyzed with various statistical methods suitable for big data.

The results of the thesis confirm the findings of earlier studies showing that energetic electron precipitation decreases ozone and affects the temperature in the northern polar stratosphere during winters and strengthens the westerly wind surrounding the polar region, the so-called polar vortex.

The thesis shows that energetic electron precipitation is the main solar-related driver and, in general, one of the most influential drivers of the northern polar vortex. The thesis also shows that energetic electron precipitation affects the occurrence of sudden stratospheric warmings, which are extreme events of wintertime stratosphere. This work shows that the effect of energetic electron precipitation is at its strongest when there are more planetary waves, disturbances affecting in the wintertime stratosphere, and they are focused on the edge of the polar vortex.

The results of the thesis improve the understanding of the atmospheric effects of energetic electron precipitation and offer better insights for modelling of these effects. This can improve, for example, long-term forecasting of weather and climate variations especially in the northern hemisphere. Therefore, the results of the thesis are also significant for the society which is dependent on climate variability in many ways.
Last updated: 23.1.2024