At the American Geophysical Union meeting in San Francisco last December, a special session was devoted to the alarmingly rapid rate of decline in the intensity of the Earth’s magnetic field over the past several centuries. Records show that this decline is typical of the period before a geomagnetic reversal. Should we be concerned? Unlike dramatic portrayals of geomagnetic phenomena in Hollywood films such as The Core, it would probably take thousands of years for the north and south poles to actually swap. This would give us plenty of time to adjust our compasses, and to allow migratory animals such as birds, which are believed to rely on the geomagnetic field for navigation, time to adapt.
However, such an event would have several important consequences. Changes in the structure and strength of the geomagnetic field can alter the paths of charged particles in the atmosphere. Although this might please aurora enthusiasts, it could also deplete the concentration of ozone in the atmosphere and cause a dramatic increase in the amount of ultraviolet radiation reaching the Earth’s surface. Indeed, some researchers have linked reversals of the geomagnetic poles with extinction events. An increase in surface radiation could also cause serious damage to communications and weather satellites in low orbits.
In the April issue of Physics World John Geissman in the Department of Earth and Planetary Sciences at the University of New Mexico describes the geomagnetic flip in more detail.