Satellites in low-Earth orbit over Southern Africa are already showing signs of radiation damage
BONNY SCHOONAKKER © Sunday 18 Jul 2004
SOUTHERN Africa is experiencing weird vibes, according to scientists studying one of the more profound upheavals awaiting planet Earth.
This forthcoming revolution is a reversal in the Earth's magnetic field, an event that occurs every 500 000 years or so.
Signs that the reversal is about to happen again are nowhere more apparent than over Southern Africa, according to Dr Pieter Kotze, head of the geomagnetism group at the Hermanus Magnetic Observatory in the southern Cape.
Satellites in low-Earth orbit over Southern Africa are already showing signs of radiation damage suffered as a result of the Earth's magnetic field weakening above our part of the planet. The field forms the magneto sphere, which, like the Earth's ozone layer, protects the planet from the sun's harmful radiation.
Other symptoms destined to become apparent in the years ahead include the aurora australis, or southern lights. Usually seen only over the South Pole, these will become visible closer to the equator as the Earth's magnetic field weakens and disappears. Eventually, on past form, the field will reappear but with magnetic north and south pole changing places, as they have done for billions of years.
According to an article in the New York Times this week, the change will be devastating for migratory animals such as loggerhead turtles, which use the Earth's magnetic field to migrate 8 000km around the Atlantic. Bees, swallows, cranes, salmon, homing pigeons, frogs and eagles may also lose their way between breeding and feeding grounds.
Humans will suffer, too. The (temporary) disappearance of the magnetic field ahead of its reversal will lead to increased occurrences of radiation-induced cancer, Kotze said.
Commenting on the New York Times report, Kotze said that the decay in the Earth's magnetic field was becoming increasingly apparent in "the South Atlantic anomaly", a huge deviation in the Earth's magnetic field discovered with the help of the Hermanus Magnetic Observatory.
This month, the European Space Agency (ESA) approved a multimillion-euro space mission, called Swarm, to measure the anomaly, which stretches from Southern Africa towards South America.
The ESA's scientists believe that this anomaly, as revealed by the occasional "geomagnetic jerk" to which our part of the world is prone, will provide a clue to predicting the next "flip" in the Earth's magnetic field, now 250 000 years overdue - as these things go. Three ESA satellites, flying in low-Earth orbit (400km to 500km up) after their launch in 2009, will measure the variation over Southern Africa.
The observatory has also recorded a faster-growing deviation between true north and magnetic north over Southern Africa during the past 10 years, drifting steadily westward. Taken together, the blip and this drift point to an imminent reversal in the Earth's north-south magnetic alignment.
"W e should be able to work out the first predictions by the end of the [Swarm] mission," Gauthier Hulot, an ESA geophysicist and a colleague of Kotze's, told the New York Times.
The discovery of the "anomalous field behaviour over Southern Africa" drew wide attention, reported the US newspaper, because "it seemed consistent with what the [ESA's] computer simulations identified as the possible beginnings of a flip".
Kotze said that, "these are all indications that we have conditions similar to the last reversal, 780 000 years ago. So it means that we are due for another one soon." In geological terms, however, "soon" could mean anytime between tomorrow and the next 3 000 years.
Kotze said the anomaly was the result of "things happening" far below the Earth's surface.
At the boundary between the mantle and the outer core (more than 3 000km below Southern Africa) disruptions were occurring in the flow of the Earth's liquid outer core (mostly iron), he explained. This created "a reverse dynamo situation", which is becoming increasingly apparent as variations in the magnetic field above the Earth's surface.
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