Power spectra of cosmic ray variations in the region of 3x10-8-10-4 Hz

The power spectral density of cosmic ray (CR) fluctuations observed at ground level during the years 1978 to 1981 has been calculated. The investigated frequency range consists of two parts, with a transient region of approx. 10-6 to 10-5 Hz. In the range of higher frequencies the CR intensity fluctuations are directly linked with the pulsations of the turbulent interplanetary magnetic field. On the other hand low-frequency fluctuations of CR intensity are caused by the diffusion fluxes of particles defined by the asymmetric part of the diffusion tensor (e.g. drift fluxes). Against this ''background'' CR fluctuations are observed contributing to aperiodic phenomena of the CR distribution (e.g. the Forbush decreases). It is indicated that for the computing power spectra the cross covariance analysis showed be used to eliminate fluctuations connected with either local differences or differences of apparatus. (author)