We have conducted an extensive experimental study on the subject of near ground atmospheric electricity. The main objective was to gain more understanding of this particular aspect of atmospheric phenomena, while testing the possible application to cosmic ray research. The results in atmospheric electricity show that there are certain patterns in ion grouping such as the size and lifetime. The average lifetime of ion group is 0.7 seconds and the average size is about 10 meters at our experimental site. Ultrahigh energy cosmic ray air showers should create sizable slow atmospheric electric pulses according to our theoretical calculations. Preliminary studies on air showers with total particle number N equal or greater than 10⁵ (10¹⁵ eV) have yielded strong evidence that slow atmospheric current pulses are associated with air showers. The theory and the experiment agree with each other fairly well when we average over large numbers of events. With our current experimental arrangement, when the air shower exceeds a certain size, the system response saturates. Therefore it is extremely desirable in future research that the counter array be designed for a much higher threshold level, since this prototype experiment indicates that interesting data would be obtained. Another reason for further experimental research being directed toward ultrahigh energy, e.g., N ≥ 10⁷ (10¹⁷ eV) and higher, is to establish a calibration of the slow atmospheric electric signals generated by cosmic rays as a function of primary cosmic ray energy and core location. This type of slow atmospheric electric signal, if fully understood and calibrated, offers a new and potentially less expensive technique to observe ultrahigh energy cosmic ray events, which hold some fundamental keys to the knowledge of the universe on a large scale.

The goal of this thesis is to improve our knowledge on energetic particle precipitation into the Earth’s atmosphere from the thermosphere to the surface. The particles origin from the Sun or from temporarily trapped populations inside the magnetosphere. The best documented influence of solar (high-) energetic particles on the atmosphere is the Ozone depletion in high latitudes, attributed to the generation of HOx and NOx by precipitating particles (Crutzen et al., 1975; Solomon et al., 1981; Reid et al., 1991). In addition Callis et al. (1996b, 2001) and Randall et al. (2005, 2006) point out the importance of low-energetic precipitating particles of magnetospheric origin, creating NOx in the lower thermosphere, which may be transported downwards where it also contributes to Ozone depletion. The incoming particle flux is dramatically changing as a function of auroral/geomagnetical activity and in particular during solar particle events. As a result, the degree of ionization and the chemical composition of the atmosphere are substantially affected by the state of the Sun. Therefore the direct energetic or dynamical influences of ions on the upper atmosphere depend on solar variability at different time scales. Influences on chemistry have been considered so far with simplified precipitation patterns, limited energy range and restrictions to certain particle species, see e.g. Jackman et al. (2000); Sinnhuber et al. (2003b, for solar energetic protons and no spatial differentiation), and Callis et al. (1996b, 2001, for magnetospheric electrons only). A comprehensive atmospheric ionization model with spatially resolved particle precipitation including a wide energy range and all main particle species as well as a dynamic magnetosphere was missing. In the scope of this work, a 3-D precipitation model of solar and magnetospheric particles has been developed. Temporal as well as spatial ionization patterns will be discussed. Apart from that, the ionization data are used in different climate models, allowing (a) simulations of NOx and HOx formation and transport, (b) comparisons to incoherent scatter radar measurements and (c) inter-comparison of the chemistry part in different models and comparison of model results to MIPAS observations. In a bigger scope the ionization data may be used to better constrain the natural sources of climate change or consequences for atmospheric dynamics due to local temperature changes by precipitating particles and their implications for chemistry. Thus the influence of precipitating energetic particles on the composition and dynamics of the atmosphere is a challenging issue in climate modeling. The ionization data is available online and can be adopted automatically to any user specific model grid.