Improved cosmic ray ionization model for the system ionosphere-atmosphere - Calculation of electron production rate profiles

The effects of galactic cosmic rays (CRs) in the middle atmosphere are considered in this work. We take into account the CR modulation by solar wind and the anomalous CR component also. In fact, CRs determine the electric conductivity in the middle atmosphere and influence the electric processes in itin this way. CRs introduce solar variability in the terrestrial atmosphere and ozonosphere-because they are modulated by solar wind. A new analytical approach for CR ionization by protons and nuclei with charge Z in the lower ionosphere is developed in this paper. For this purpose, the ionization losses (dE/dh) according to the Bohr-Bethe-Bloch formula for the energetic charged particles are approximated in three different energy intervals. More accurate expressions for CR energy decrease E(h) and electron production rate profiles q(h) are derived. The obtained formulas allow comparatively easy computer programming. q(h) is determined by the solution of a 3D integral with account of geomagnetic cut-off rigidity. The integrand in q(h) gives the possibility for application of adequate numerical methods-in this case Gauss quadrature, for the solution of the mathematical problem. Computations for CR ionization in the middle atmosphere are made. In this way the process of interaction of CR particles with the upper and middle atmosphere are described much more realistically. The full CR composition is taken into account: protons, helium (a-particles), light L, medium M, heavy H and very heavy VH group of nuclei. All computations are made for geomagnetic cut-off rigidity R = 1 GV in the altitude interval 15-120 km. The COSPAR International Reference Atmosphere CIRA'86 is applied in the computer program for the neutral density and scale height values. The proposed improved CR ionization model will contribute to the quantitative understanding of solar-atmosphere relationships. (C) 2007 Elsevier Ltd. All rights reserved.