Cosmic ray-induced ionization in the atmosphere: spatial and temporal changes

Detailed calculations of the time-variable spatial distribution of cosmic ray-induced ionization of the lower atmosphere are presented using a physical model. Using the differential energy spectrum of cosmic rays obtained from the worldwide neutron monitor network since 1951 and taking into account also the slow changes in the geomagnetic dipole, we have calculated the corresponding 3D (geographical coordinates and altitude) equilibrium ion concentration in the lower atmosphere as a function of time for the period 1951–2000. A comparison to the results of measurements validates the calculation method, as the calculated cosmic ray-induced ionization reproduces in general the observed altitudinal and latitudinal profiles of the ion concentration. The results of the present work provide a basis for a quantitative study of the solar–terrestrial relationships on long time scales.