The response of middle atmospheric ozone to solar proton events in a changing geomagnetic field.

This work presents investigations of possible impacts of geomagnetic field variations on middle atmospheric ozone responses to solar proton events (SPEs) by the means of atmospheric modelling.On geological time-scales, the Earth's magnetic field is subject to significant variations which alter the regions in which charged particles can enter the atmosphere. The precipitating particles lead to the formation of reactive radicals which in turn destroy ozone in catalytic cycles. The existing atmospheric model has been enhanced by modifications of the mesospheric chemistry scheme, and by the development of an ion chemistry model. The present-day magnetic field configuration and five other scenarios have been analysed. In all magnetic shielding scenarios the ozone destructions due to SPEs are most pronounced in the polar regions. They are found to increase with the size of the magnetic cusp and with its nearness to the polar regions.