The Earth's magnetic field is weakening and scientists don't know why

Earth’s magnetic field is weakening, and no one is sure why A weaker magnetic field will make the planet more susceptible to solar radiation and put space equipment at risk.

TORONTO — A mysterious anomaly is causing the Earth’s magnetic field to weaken between South America and Africa, and scientists don't know why.

Data collected by the European Space Agency (ESA) and published in May notes that the affected area, known as the South Atlantic Anomaly, has seen the magnetic force weaken by nearly 9 per cent over the last 200 years.

There is a lot of speculation about this phenomenon is happening, but according to York University astronomy and physics professor Paul Delaney, the anomaly could be caused by a regular reversal of Earth’s magnetic field.

"If you go back through the geologic record you can actually map out the U.S. magnetic field as a function of time really easily. We know that the Poles, our North and South Poles magnetically flip every, on average, 500,000 years," Delaney explained to CTV's Your Morning on Tuesday.

He added that the last time the Earth’s magnetic field reversed was approximately 780,000 years ago. Delaney said the current measurement of the weakening field may suggest that the Earth is about to go through a reversal, but it is unlikely.

"The problem here is that the mechanism generates that magnetic field, and why it reverses is a random type of event. It doesn't happen periodically, so we can't really say that this weakening is a precursor to the actual reversal. It might be, but it probably isn't," Delaney said.

The ESA estimates that the field loses approximately five per cent of its strength every decade but the agency hasn't been able to pinpoint how close it may be to its next reversal.

Delaney said the region in question stretches from the northern portion of South America across the Atlantic Ocean into Africa. That area comprises dense rock that forms part of the Earth’s mantle, called the African Large Low Shear Velocity Province.

Scientists have also suggested that magnetic field changes may be due to the changes in this dense rock which accounts for the motion of tectonic plates at the surface level.

"The main problem is that the magnetic field of the planet is relatively weak there, because the centre of the magnetic field is set away from that region," Delaney said.

"If you think of the Earth as a big sphere, and you put a nice dot in the middle of that sphere, that is where the rotation axis passes, but the magnetic axis passes a few hundred kilometres away from that, away from South America, meaning that the magnetic field that we're generating inside our planet is weakest there," he explained.

While the Earth's magnetic field protects humans from solar radiation, Delaney said the most significant effects of the weakening magnetic field are limited to technical malfunctions on board satellites and space crafts.

"The problem is that ou radiation belts, full of charged particles, are a lot closer to the surface, and that means it can cause problems for satellites, and people are concerned, all because the magnetic field is the weakest at that location," Delaney said.

He added that humans don't currently have any cause to be concerned.

"Charged particles of course are not good for you -- you do not want to be bombarded by high-speed electrons, protons and other ions. That's not good for any life form," Delaney said.

"The magnetic field of our planet tends to create a huge bubble or a cushion around us, that deflects away most of these charged particles. Some of it does leak in and gets caught in the Van Allen radiation belt but very little gets to the surface of the Earth. That’s a good thing."

However, Delaney said the weakening could start to cause problems for humans if it expands.

"If the magnetic field weakens continuously, in fact if the magnetic field turned off, that would really be bad. As long as we have any measure of magnetic field, even a weakened field, it protects us in large measure from these dangers from space," he said.

If the magnetic field were to disappear completely, Delaney said humans will "really have a problem" because it would increase exposure to higher levels of ultraviolet radiation that can be harmful to humans.

The ESA said it will continue to monitor the weakening magnetic field using its Swarm satellites.

"The mystery of the origin of the South Atlantic Anomaly has yet to be solved," the space agency said in a statement. "However, one thing is certain: magnetic field observations from Swarm are providing exciting new insights into the scarcely understood processes of Earth's interior."