The chemical composition of the middle atmosphere can be strongly influenced by Solar Proton Events (SPEs) and Energetic Electron Precipitation Events (EEPs). These events are sources of odd hydrogen and nitrogen, which both contribute to ozone loss in the middle atmosphere. Due to its long lifetime, significant amounts of odd nitrogen and hydrogen are produced by large particle events in the mesosphere and the upper stratosphere can be transported down into the middleand lower stratosphere during polar winter, where e.g. odd nitrogen is a key species in ozone loss. Thus large particle events...