Implications of energetic particle precipitation events for the temperature and dynamics of the atmosphere - a model study

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The idea of this project is to investigate the thermal and dynamical changes related to large energetic particle precipitation events. Energetic particle precipitation influences the heating and cooling rates of the middle and upper atmosphere directly by different processes at different altitudes: (i) by Joule heating in the thermosphere and upper mesosphere, (ii) by chemical heating in the upper mesosphere, and (iii) due to radiative heating and cooling of ozone in the mesosphere and upper stratosphere. While the first two effects are fairly short-lived and will impact the atmosphere only during the particle event, the last effect, based on ozone loss, can continue for several weeks to months and propagate down into the mid-stratosphere during polar winter. Changes in heating / cooling rates will affect the temperature, and therefore also the large-scale circulation and wave-propagation in the middle atmosphere. While energetic particle precipitation events are well known to greatly disturb the chemical composition of the middle atmosphere, little is known about their potential to influence atmospheric temperatures and dynamics on seasonal or even longer time scales. However, a better understanding of these processes could be relevant for climate models. We propose to use the Bremen 3d CTM to calculate changes of the chemical composition of the middle atmosphere related to large energetic particle events for the period 1997 - 2007. From these results, changes to the radiative and chemical heating rates in the middle atmosphere will be derived and imposed onto the mechanistic general circulation model KMCM to assess the impact of these changes on atmospheric temperatures and dynamics.