Ionization effect of nuclei with solar and galactic origin in the Earth atmosphere during GLE 69 on 20 January 2005

Abstract

The ground level enhancement 69 on January 20, 2005 is the second largest event in the history of cosmic ray measurements. Solar protons cause an excess of ionization in the atmosphere, specifically over polar caps following major solar disturbances. At present the contribution of proton nuclei is highlighted. In this study is estimated the ion rate production in the atmosphere due to a major solar energetic particle (SEP) event on 20 January 2005 produced by various solar nuclei, namely proton, Helium, Oxygen and Iron. The contribution of light, middle and heavy nuclei of solar and galactic origin is explicitly obtained. The spectra of the nuclei are considered on the basis of GOES 11 satellite measurements. The Forbush decrease during the event is also explicitly considered. The ionization effect in the Earth atmosphere is obtained for various latitudes on the basis of a full Monte Carlo simulation of induced atmospheric cascade by solar and galactic cosmic ray particles. The evolution of atmospheric cascade is performed with the CORSIKA 6.52 code using FLUKA 2006b and QGSJET II hadron interaction models. The atmospheric ion rate is obtained for 40°N, 60°N and 80°N latitudes. The time evolution of obtained ion rates is presented. It is demonstrated that the ionization effect is significant in sub-polar and polar atmosphere and moderate at middle latitudes.