Climate change and the accompanying global warming have been the subject of intensive research for several years. Although the anthropogenic influences are largely understood, climate models still show uncertainties in consideration of the natural processes. In particular, the coupling mechanisms between atmospheric layers and solar influence so far have not been sufficiently understood. An important role is played by the altitude range of 10 to 110 km, the so-called the middle atmosphere. In this context, the term “solar influence” refers not only to the incident sunlight, but also to charged particles originating from the Sun (mostly protons and electrons).
In the middle atmosphere, this solar influence leads to changes in the chemical composition. Most of the atmospheric constituents are only present in small quantities (<0.01%), and the corresponding changes are also small. However, these small changes in the trace gas concentrations can greatly influence the whole atmosphere. For example, an increase in charged particle fluxes in the middle atmosphere initially leads to an ozone depletion. Ozone, in turn, strongly absorbs the incident sunlight which causes local radiative heating of the middle atmosphere. The resulting temperature changes are generally balanced by the winds in the atmosphere. Consequently, changes in temperature also affect the prevailing winds. Thus, an improved knowledge of the changes in the trace gas concentrations and the underlying natural processes result in a better understanding of the whole atmosphere.
We investigate the influence of solar activity on the whole atmosphere using satellite data and numerical models with different complexities.
Direct measurements of constituents in the altitude region between 80 and 110 km are relatively rare. Thus, global satellite observations of the atmospheric airglow are used to derive trace gas concentrations and air temperature.
We also apply our knowledge about the Earth’s atmosphere to atmospheres of exoplanets.