Earth’s history of polar reversalsEarth’s magnetic field is created by its rotation, as well as the rotation of our planet’s core. This radiation thins Earth’s ozone layer and lets in more ultra violet (UV) and the interaction of these particles with the Earth’s magnetic field also results in aurora. Scientists believe that it is caused by some instability in the processes that generate Earth’s magnetic field. During the Laschamps excursion, Earth’s magnetic field reduced in size to about 10 percent of its current strength. As a result, Earth’s magnetic poles drooped down near the equator and the magnetic field lines expanded.