Time evolution of ionization effect due to cosmic rays in terrestrial atmosphere during GLE 70

• Computation of ion production rate during GLE 70 on 13 December 2006 in a polar and a sub-polar region.
• The time evolution of SEP spectra and anisotropy is explicitly considered.
• The ion production rate is computed at several altitudes.
• The relative to average of GCR ionization effect is estimated.

In the last years the possible effect of solar variability on atmospheric physics and chemistry is highly debated. In most of the proposed models the role of ion production in the atmosphere due to cosmic rays is significant. At present, effects on minor constituents and aerosols are observed over polar regions during major solar events. According to recent findings for such a study it is necessary an essential increase of ion production, specifically during the winter season. Therefore, the ground level enhancement on 13th of December 2006 is appropriate for such a study. Here, we compute the ion production on 13th of December 2006 on the basis of a full target model based on Monte Carlo simulations. The ion production is computed on a step ranging from 10 to 30 min throughout the event. The spectral and angular characteristics of the solar protons are explicitly considered as well as their time evolution. The ionization effect is computed at several altitudes above the sea level, namely 25 km, 18 km, 15 km, 12 km and 8 km in a sub-polar a and polar region, where the effect is maximal. Several applications of the obtained results are discussed.