This work is an extension of a phenomenological study of the middle polar atmosphere response to severe solar energetic particle (SEP) events. The present work is focused on evaluation of the potential influence of atmospheric ionization caused by solar cosmic rays upon the chemical composition of polar stratosphere. We have performed thorough analysis of variations of the daily profiles of NO2 and ozone by the SAGE III and SAGE II instruments for North Polar Regions. We found statistically significant changes in the chemical compositions associated with the SEP events.