Abstract. An analytical and numerical approach for penetration and ionization of cosmic ray nuclei with charge Z in the planetary ionospheres and atmospheres is considered. The electron production rates are calculated using new formulas, which couple the five main energy intervals in the ionization losses function (dE/dh). This is a 5-interval function, which performs a better approximation of the measurements and the experimental data in comparison with previous results. The geomagnetic cut-off rigidities and the energy decrease laws for the different intervals are used for creating of an intermediate transition energy region, which performs the coupling of the 5 intervals in the ionization losses function. A new 6-th energy interval for charge decrease in lower energies is taken into account. Ionization profiles in the Earth atmosphere due to a large solar energetic particle event on 20 January 2005, produced by various nuclei, namely Helium, Oxygen and Iron are presented also. The spectra of the nuclei are explicitly considered. A full Monte Carlo simulation of the cosmic ray atmospheric cascade with CORSIKA 6.52 code using FLUKA 2006 and QGSJET II hadronic interaction models is carried out. The energy deposit in the atmosphere is obtained. The atmosphere is divided per 10 g/cm², which permits good precision. The ionization rate is compared for different latitudes, namely for 40⁰N, 60⁰N and 80⁰N. The contribution of various nuclei as a function of the latitude is widely discussed.

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