Researchers analyzing a decade of geomagnetic measurements from the British Geological Survey have identified dozens of mysterious signal candidates that could correspond to ultralight axions or dark photons. The team proposed using the Earth-ionosphere cavity as a giant resonator to probe invisible matter.
Physicists have spent decades searching for the invisible substance that holds the cosmos together. Accounting for an estimated 85 percent of the universe’s matter, dark matter remains undetectable to direct observation because it does not reflect, absorb, or emit light. Scientists traditionally rely on gravitational effects on galaxies or turn to massive laboratory tanks to capture rare particle interactions.
A team of researchers took a radically different approach. By modeling the natural space between Earth’s surface and the ionosphere, the team discovered a planetary-scale resonance capable of amplifying electromagnetic waves within specific frequency ranges.
How Researchers Used Earth as a Resonator
The novel search targets ultralight particles such as axions and dark photons, which are theorized to be roughly 19 to 21 orders of magnitude lighter than an electron. While axions were originally proposed in the 1970s to solve separate particle physics problems, researchers realized they could also account for dark matter if they fall within a specific mass range.
Previous theoretical frameworks could only reliably describe frequencies below 1 Hz, leaving higher ranges unexplored. To bridge this gap, investigators from Kyoto University, Hiroshima University, and Nihon University developed a new theoretical framework incorporating atmospheric electrical conductivity. Their calculations demonstrated that the Earth-ionosphere cavity amplifies signals near 8 Hz and supports reliable predictions up to about 30 Hz.
Taruya explained that the Earth-ionosphere cavity acts as a natural resonator that amplifies electromagnetic waves right around the mass range we wanted to probe.
To test the theory, the researchers evaluated geomagnetic data gathered between 2012 and 2022 by the British Geological Survey’s Eskdalemuir Observatory.
Signals, Statistics, and Distinguishing Dark Matter Candidates
After removing artificial noise from the decade-long dataset and applying statistical filters, the team identified multiple candidate signals.
The underlying physics offer a way forward. Axion signals depend on Earth’s magnetic field to generate electromagnetic waves, meaning their strength should vary geographically—weakening near the poles and peaking around Southeast Asia. Dark photons, by contrast, should register at nearly identical strengths globally. Because the British Geological Survey data originated from a single UK observatory, verifying this distinction requires a worldwide network of observations.
Underground Experiments Record Separate Particle Events
While researchers in Japan analyzed planetary magnetic fields, separate teams monitored deep-underground tanks filled with liquid xenon.
The LZ detector utilizes 10 tonnes of ultrapure liquid xenon.
Examining 220 days of data, researchers found an event occurring on June 16, 2023, that does not fit the description of any other known particle interaction.
Despite the excitement, researchers caution against premature conclusions. Statistical analyses indicate the event has only about a 1-in-400 chance of being a statistical fluke—a 2.6-sigma result—well short of the 5-sigma gold standard required for a formal scientific discovery.
