Abstract
In the recent geological past, Earth's magnetic field reduced to ~10% of the modern values and the magnetic poles shifted away from the geographic poles, causing the Laschamps geomagnetic excursion, about 41 millennia ago. The excursion lasted ~2000 years, with dipole strength reduction and tilting spanning 300 years. During this period, the geomagnetic field's multipolarity resembled outer planets, causing rapid magnetospheric changes. To our knowledge, this study presents the first space plasma analysis of the excursion, linking the geomagnetic field, magnetospheric system, and upper atmosphere in sequence using feedback channels for distinct temporal epochs. A three-dimensional reconstruction of Earth's geospace system shows that these shifts affected auroral regions and open magnetic field lines, causing them to expand and wander toward lower latitudes. These changes likely altered the upper atmosphere's composition and influenced anthropological progress during that era. Looking through a modern lens, such an event would disrupt contemporary technology, including communications and satellite infrastructure.