Energetic particles precipitating into the atmosphere at high latitudes can have a significant impact on atmospheric composition, temperatures and dynamics. Primary collisional processes lead to excitation, dissociation and ionization of the most abundant species (N2, O2, O), a source of nitric oxides mainly in the upper mesosphere and lower thermosphere (70--150 km) related to high-energy electron precipitation from the aurora and radiation belts, but extending down to the upper stratosphere (about 40 km) in strong solar proton events and geomagnetic storms. However, a larger source of nitric oxides in the high-latitude stratosphere is the so-called "Energetic particle precipitation indirect effect" due to downward transport in large-scale descent motions during polar winter. As nitric oxides contribute to catalytic ozone desctruction in the middle stratosphere (30--45 km), this indirect effect also affects high-latitude mid-stratosphere ozone during polar winter and spring. Ozone is the main driver of radiative heating and cooling in this altitude region, and this modulation of ozone by energetic particle precipitation therefore starts a chain of dynamical coupling mechanism leading to changes in temperatures and wind fields over wide areas of the atmosphere, possibly even down to tropospheric weather systems. In this talk, the most important processes related to particle precipitation will be explained, summarizing the state-of-the art of satellite observations and modelling studies.
Mode of presentation: oral (Need to be confirmed by the SOC)