Though there is little scientific or academic disagreement as to the reality of the existence of geomagnetic polar shifts and reversals, there is much speculation and theorizing as to what the hypothetical impacts and effects of such an event would be; and still more controversial is just how hypothetical such an eventuality actually is.
The magnetic field waxes and wanes, poles drift and, occasionally, they flip. Every so often, our planet’s magnetic poles reverse polarity. Earth’s magnetic field reverses every few thousand years at low latitudes, a geologist funded by the National Science Foundation (NSF) has concluded. Reversals take a few thousand years to complete, and during that time—contrary to popular belief—the magnetic field does not vanish.
However, we still don’t know for certain how the Earth’s magnetic field is generated and maintained. The origin of the magnetic field and its reversals is one of the oldest problems in physics, and one of the most active areas of research in geophysics today. Scientists believe Earth’s magnetic field is generated deep within our planet.
Roughly speaking, Earth is like a chocolate-covered cherry—layered, with liquid beneath the surface and a solid inner core. Beneath the planet’s relatively thin crust is a thick solid layer called the mantle. The inner core has its own ocean: a very deep layer of liquid, believed to be composed of swirling convection flows of molten iron and nickel, known as the outer core. The Earth’s magnetic field is understood to come from this ocean of iron, which is an electrically conducting fluid in constant motion. The Earth’s magnetic field is created deep within our planet’s outer core through what is known as the geodynamo. There, the heat of the Earth’s hot solid inner core churns the liquid outer core sitting atop it like water on a hot stove. These complex motions generate our planet’s magnetism through a process called the dynamo effect. The churning acts like convection, which generates electric currents and, as a result, a magnetic field. This idea that turbulent activity at the outer core of the planet generates its magnetic field currently dominates scientific thinking.
Our planet’s magnetic field varies with time, indicating it is not a static or fixed feature. Instead, some active process works to maintain the field. That process is most likely a kind of dynamic action in which the flowing liquid material in the outer core generates the magnetic field, geologists believe.
Most scientists believe Earth’s magnetic field is sustained by a complex self-sustaining interaction known as the “geomagnetic dynamo”. The term describes the theoretical phenomenon believed to generate and maintain Earth’s magnetic field. According to general accepted theory—the dynamo theory—interactions between the churning convecting flow of molten iron in the Earth’s outer core and the magnetic field generate electrical current that, in turn, creates new magnetic energy that sustains the field. It is known, however, that the mechanism of magnetic field generation is related to Earth’s rotation. The rotation of planets may be among the necessary conditions for the formation of their magnetic fields. However, rotation alone is insufficient for the creation of a planetary magnetic field.
Figuring out what happens as the field reverses polarity is difficult because reversals are rapid events, at least on geologic time scales. A major uncertainty, however, has remained regarding how long this process takes.
Scientists have been observing changes in the direction of Earth’s magnetic which took place recently as well as in the distant past. The study of Earth’s past magnetism is called paleomagnetism. The magnetic field has exhibited frequent but dramatic variation at irregular times in the geologic past: It has completely changed direction. The geological record confirms that magnetic field reversals have occurred in the past. Earth’s magnetic field has flipped many times over the last billion years, according to the geologic record.
It is not only the direction but also the strength of the magnetic field that is a concern. Earth’s magnetic field—the force the protects us from deadly radiation bursts from outer space—is weakening dramatically. While nobody quite knows why this is occurring, the weakening of Earth’s magnetism is believed by many of the most respected scientists in the field of geomagnetism to be one of the factors predictive of a pole realignment, a precursor, and perhaps even a forecaster, of magnetic polar reversal sometime in the near future.