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by Spektrum der Wissenschaft
Earth's magnetic field to detect dark matter
5.2.2026
Translation: machine translated
The Earth's magnetic field as a gigantic detector? Physicists are using existing networks of sensors to detect evidence of dark matter.
What is the mysterious dark matter, which makes up around a quarter of our universe, made of? Researchers have now found an unusual approach to answering this question: the Earth's magnetic field could serve as a giant sensor that could possibly be used to detect these mysterious particles. As a team led by Ariel Arza from Nanjing Normal University describes in the journal «Physical Review Letters», the Earth's magnetic field could contain evidence of dark matter.
As the name suggests, dark matter is not yet visible to the scientific community. The mysterious particles can therefore only interact very weakly with their surroundings, which is why they most likely carry no - or only a very weak - electrical charge. There are several different theories as to what dark matter could actually be: dark photons, sterile neutrinos, axions ... There are hardly any limits to the imagination of researchers. Ultra-light particles with only a fraction of the electron charge are also conceivable. And Arza's team now wants to track them down.
Because such particles could annihilate each other in the planet's magnetic field and generate an electric current with its own magnetic field. Although this would be around a million times smaller than that of the Earth, it would be detectable through characteristic temporal fluctuations. The lighter the hypothetical particles, the stronger the signal should be.
The experts did not set up any complex new experiments for their search for traces, but were able to draw on existing sensors. Among other things, they used data from the research project SuperMAG, which operates around 500 measuring stations worldwide to determine the Earth's magnetic field in detail. These were originally installed to monitor geomagnetic activity.
Analysing the data presented the team with particular challenges. The researchers had to filter out the natural noise of the Earth's magnetic field, as the magnetic field is disturbed by solar winds, ionospheric currents and human activity. To do this, they developed a sophisticated method of analysis that utilises the characteristic spatial pattern of the suspected signal - a kind of fingerprint that should extend over the entire surface of the earth. But the experts found no trace of such a signal.
However, this has enabled the team to place the most precise constraints to date on the possible electrical charge of dark matter particles. If they have a mass of 10-18 to 10-14 electron volts (a mass unit commonly used in particle physics), the researchers were able to refine the previous constraints on the charge by more than 13 orders of magnitude: the particles are therefore only likely to have an electric charge that is less than 10-30 times the electron charge.
The new work shows how natural phenomena can be used as detectors for fundamental physics - which opens up completely new possibilities. Unlike in laboratory experiments, where the signal strength is limited by the size of the detector, the researchers in this work benefited from the enormous radius of the Earth. If this version of dark matter with an extremely weak charge actually exists, more precise measurements of the Earth's magnetic field could enable its discovery.
Spectrum of Science
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