Monday, October 11, 2021

Rapid changes in Earth's magnetic field could threaten our technologies

 Scientists already know that the Earth's magnetic field is not immobile.  Its poles move with a certain frequency and, according to new studies, with greater speed than previously imagined.  The problem is that, while protecting us from solar radiation, the movement of the magnetic field can also threaten our satellites.

 Currently, satellites that help monitor changes in the magnetic field reveal that the pole shifts are quite moderate, around a tenth of a degree per year.  But we don't know much about the behavior of magnetic poles, as studies on the subject are no more than 400 years old.  It sounds like a lot, but remember, the magnetic field has been around for 3.5 billion year.

 Over all this time, our magnetic shield may have exhibited different behaviors, including varying the speed at which the poles move.  The north and south poles have been on opposite sides in the past and this could happen again, without anyone knowing exactly when it will happen.  It won't be now, but there are signs that it won't take thousands of years, as expected before.

 To track field variations over time, scientists analyze magnetism recorded in sediments, lava flows and man-made artifacts eons ago.  Think of these objects as recorders - they contain magnetic grains that “record” the Earth's field signature as they solidify.  Analyzing them is like going back in our planet's magnetic time.

 Sediment records found in central Italy tell us that the last polarity reversal - that is, magnetic north and south switched places - happened nearly 800,000 years ago.  This suggests that field changes can become rapid and reach one degree per year.

 New research used physics-based computer models of the magnetic field generation process, combining it with a reconstruction of global variations in the field over the past 100,000 years.  The basis for this reconstruction is a compilation of measurements taken on sediments, lavas and artifacts.  This showed that changes in the direction of the Earth's magnetic field reached rates of up to ten degrees per year - ten times greater than the fastest changes currently reported.

 What does this mean in impacts in today's world?

 First, we can rule out the possibility that this is life threatening.  Proof of this is the Laschamp event, the first geomagnetic excursion (pole shift from the polar region to the earth's equatorial region, without resulting in a pole shift) that 41,400 (± 2,000) years ago, and we survived it!  How we know?  The placement of the magnetic field was recorded in lava from volcanoes near the French Clermont-Ferrand district.  The Laschamp event was the first known geomagnetic excursion and remains the most studied.

 However, the Earth's rapid magnetic changes could threaten the current lifestyle of a society that is highly dependent on technology and electronic infrastructure.  Spatial weather events caused by the interaction between the magnetic field and solar radiation can disrupt satellite, GPS and power grid communications.

 The problem is that these spatial weather events tend to happen more in regions where the magnetic field is weak, and it can weaken when it changes quickly.  Unfortunately, we cannot predict this acceleration and dips in field strength just by monitoring the direction of the field.  It will take work using advanced computer simulations to overcome this problem.

 Rapid changes in the magnetic field can happen quickly and have a big impact - although these are the rarest events.  Scientists consider these a type of “black swan event”.  In other words, unpredictable, which happen quickly and change the scenario dramatically, so that they present great challenges to managers.

 One possible way to predict large accelerated changes in the magnetic field is to use physics-based models of how the field behaves.  But there's still a lot to learn, like the "speed limit" of the Earth's magnetic field.  Rapid changes have not yet been observed directly during a polarity reversal, not even during an excursion.  But we must wait for them, as they will happen.  And when the day comes, it is not only necessary to know how to deal with the situation, but also to record everything in detail for posterity.

 If the field does become globally weak during a more drastic change, it will be worrisome.  The economic cost of a collapse of the US power grid due to a space-climate event alone has been estimated at around a trillion dollars.  On a global scale, it would be unimaginable.  The threat is serious enough that space climate is a high-priority issue for agencies that study space and our planet - and, right between us, there should be no savings in research efforts and investments in this area.


 1- Illustration of the Earth's magnetic field (Image: DESY)

 2- Illustration of the magnetic field polar reversal process (Image: NASA)

 3- How the Earth's magnetic field works and the position of the north and south poles, both geographic and magnetic (Image: Getty Images)

 Credits: Canaltech

 Source: The Conversation


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