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Scientists have used Earth’s natural electromagnetic environment to search for two leading dark matter candidates, ultralight axions and dark photons, in a new study that could expand the hunt for the mysterious substance.
Researchers from Kyoto University, Hiroshima University and Nihon University examined whether the cavity formed between Earth’s surface and the ionosphere could act as a natural detector. The region can resonate with electromagnetic waves, potentially amplifying signals produced by extremely light dark matter particles.
The team developed a new theoretical framework that accounts for the electrical conductivity of the atmosphere. Their calculations suggest the Earth-ionosphere cavity can amplify signals around 8 hertz and allow reliable predictions up to about 30 hertz, extending previous work that was largely limited to frequencies below 1 hertz.
The researchers also found that the two candidate particles could produce distinct signals. Axion-related signals are expected to vary by location, with stronger signals potentially appearing in Southeast Asia, while dark photon signals should have nearly uniform strength worldwide.
To test the theory, the team analysed about a decade of geomagnetic data collected from 2012 to 2022 at the British Geological Survey’s Eskdalemuir Observatory in Scotland. They removed artificial noise and searched for persistent, narrow-frequency signals that could indicate dark matter.
They conducted separate searches for dark photons, which can generate electromagnetic waves without requiring a magnetic field.
Dark matter is believed to account for about a quarter of the universe’s total energy content, but its composition remains unknown. The study offers a novel way of using Earth itself as part of the search for the elusive substance.
