Scientists from Japanese universities have developed a novel approach to detecting dark matter by leveraging Earth’s natural electromagnetic environment. Rather than relying solely on laboratory equipment, the team proposed using the region between Earth’s surface and the ionosphere as a large-scale detector, since this cavity naturally resonates with electromagnetic waves in frequencies relevant to the search for ultralight particles.
The researchers focused on two leading dark matter candidates: ultralight axions and dark photons, which would be extraordinarily light compared to electrons. Previous theoretical models could only reliably describe frequencies below 1 Hz, leaving much of the potentially useful frequency range unexplored. To address this limitation, the team developed a new theoretical framework incorporating atmospheric electrical conductivity, enabling reliable predictions for frequencies up to approximately 30 Hz. Their model also predicted distinct signatures for each particle type: axion signals should vary by location with strongest concentrations in Southeast Asia, while dark photon signals should appear uniformly worldwide.
The researchers analyzed approximately ten years of geomagnetic measurements collected by the British Geological Survey’s Eskdalemuir Observatory. After removing artificial noise sources, they searched for steady signals within narrow frequency ranges that dark matter would be expected to produce over extended periods. The analysis yielded significantly tighter constraints on how strongly axions could interact with light—roughly 100 times more restrictive than previous ground-based experimental results and competitive with astrophysical observations from space observatories.
The dark photon analysis produced particularly noteworthy results, with researchers identifying several signal candidates that could potentially originate from dark matter. However, the source of these signals remains unknown and has not yet been confirmed as evidence of dark matter. The newly developed theoretical framework provides a foundation for expanded future searches using Earth’s natural electromagnetic properties to probe lighter forms of dark matter.
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