Geomagnetic Excursions and Reversals: Establishing their Atmospheric and Climatic Effects

The intensity of Earth’s magnetic field, which forms an important shield for our habitat, drops dramatically during geomagnetic field excursions and reversals (termed GERs). The Laschamps excursion (~41 000 years ago) occurred near during profound climatic changes that likely hadpossibly leading to drastic effects on the biosphere. While possible impacts of GERs upon the atmosphere can be theoretically expected, the magnitude, time scales, and even the direction/sign of the diverse effects on our habitat are largely unknown. The significantly weakened geomagnetic field shrinks the magnetosphere, enhancing fluxes of energetic particle fluxess from outer space reaching to the middle and lower atmosphere and even ground. The impact of GERs to another major source of energetic particles, to on the precipitation of energetic particles from the magnetosphere, e.g. from the radiation belts, is in turnalso presently unknown. The dynamics of near-Earth space and the atmosphere during GERs and their potential impacts have not yet been addressed in their full complexity, due to a lack of reliable data, precise models and interdisciplinary approaches. We will unravel key dynamics and connect physical processes in these domains during GERs and establish their environmental consequences by synergistically bringing together expertise from palaeomagnetism, magnetospheric, solar, heliospheric, atmospheric physics and climate. We will combine new geomagnetic data-based geomagnetic field models of the magnetic field state with state-of-the-art magnetospheric, atmospheric, and global Earth-system models to formfor a complete process view. To reach the goal, several breakthrough results are expected.