Charakterisierung des solaren Zyklus mittels verschiedener Beobachtungsgrößen

Abstract

As it has been found that radiation exposure at aviation altitudes is increased compared to ground, a possible health threat is of concern for airline personnel. Responsible for the increased radiation exposure in air traffic are galactic cosmic rays (GCR) originating in the interstellar space. The primary particles of GCR cause a cascade of secondary particles in the Earth’s atmosphere. The intensity of GCR is modulated by the solar cycle and is anti-correlated with the solar activity, which is proportional to the number of sunspots. This thesis deals with the characterization of the solar cycle by adequate parameters in order to estimate the intensity of GCR and therefore also the radiation exposure at aviation altitudes. Besides the neutron monitor count rates (NMCR) as an indicator of the GCR intensity and the sunspot number (SSN), the solar radio flux (SRF) was selected by calculating the correlation coefficients between the parameters. To obtain periodic structures in the time response first the dominant frequencies were determined for all quantities by using sine-fits and the fast Fourier tranform. Both methods identified for all parameters a dominant period of 11 years, which is the duration of the solar cycle. In the second part of the data processing the time lag between the parameters was investigated with three different methods. Firstly the results from the sine-fits for the corresponding data series were used, secondly a gradual shift was applied in the data series and the correlation coefficient was calculated. As the third method the cross-covariance function was employed. The results showed only slight or no temporal differences between the solar parameters (SSN, SRF) but similar time lags to the NMCR. Additionally comparing these time lags for even and odd cycles, a significant difference in the length of the time lags was observed. For even cycles a time lag of 0-5 months was found, while for odd cycles the time lag variied between 11 and 14 months. These facts indicate different conditions in the modulation of GCR for even and odd cycles and can be explained by the polarity of the global solar magnetic field.