The ground level enhancements (GLEs) due to solar cosmic rays (SCRs) are of significant
astrophysical, cosmophysical and geophysical interest for a number of planetary processes on the
Earth. In the present work the ionization rate profiles in the Earth’s atmosphere during the
outstanding ground level enhancement GLE05 on 23 February 1956, the largest one in the entire
history of observations of SCRs, are obtained. The contribution of the galactic cosmic rays
(GCRs) is also taken into account. The ionization in the atmosphere is calculated using the
energetic spectra of solar protons, GCRs and the corresponding atmospheric cascade simulation.
The spectra of solar cosmic rays are derived on the basis of ground-based measurements with
neutron monitors. This method is based on solving the inverse problem - reconstruction of SCR
spectrum on the boundary of the magnetosphere. The contemporary magnetosphere model
"Tsyganenko 01 and 03" is used in this method. The calculation of asymptotic cones (AK) held
with increments of 0.001 GV in the range of 1-20 GV. The aforementioned method is developed
in the Polar Geophysical Institute (in Apatity) of the Russian Academy of Sciences. Recent
simulations with RUSCOSMICS software package (based on GEANT4 program of CERN) are
carried out. The energy deposit of solar protons and GCRs in the atmosphere is received. The ion
production rate profiles in the stratosphere and troposphere (the region 0-40 km) are calculated
for geomagnetic cut-oﬀ rigidities 1, 2, 3 and 5 GV (i.e. polar, subpolar, higher and middle latitudes,
respectively). The so obtained ionization proﬁles are compared and thoroughly discussed.
Implementations of these results are also debated. The obtained results are important for the
improvement of the recent models of cosmic ray induced ionization in the whole atmosphere, for
the determination of electron and ion density in the middle and lower atmosphere (troposphere),
for the various atmospheric processes (as for instance in atmospheric chemistry and physics -
ozone production, global electric circuit between the ground and ionosphere), for the studies of
solar-terrestrial influences on space weather and space climate) and for many other applications.