Hunting axion dark matter signatures in low-frequency terrestrial magnetic fields

Atsushi Taruya; Atsushi Nishizawa; Yoshiaki Himemoto

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arXiv · 2504.06653

Hunting axion dark matter signatures in low-frequency terrestrial magnetic fields

Atsushi Taruya·Atsushi Nishizawa·Yoshiaki Himemoto

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Abstract

We show that Earth's natural environment can serve as a powerful probe for ultralight axion dark matter. In the presence of global geomagnetic fields, the axions with masses ranging from $10^{-15}\,{\rm eV}-10^{-13}\,{\rm eV}$ induce electromagnetic waves in the (sub-) extremely low-frequency band ($0.3-30\,{\rm Hz}$) through the axion-photon coupling. We predict the amplitude of induced magnetic fields in the Earth-ionosphere cavity, taking the finite conductivity of the atmosphere into account. This allows us to constrain the axion-photon coupling parameter, $g_{\rm a\gamma}$, from the long-term monitoring data of the low-frequency magnetic fields, resulting in a significant improvement from the previous constraints down to $g_{\rm a\gamma} \lesssim 4\times10^{-13}\,{\rm GeV}^{-1}$ for axion mass $\sim 3 \times 10^{-14}\,{\rm eV}$.

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Atsushi Taruya, Atsushi Nishizawa, Yoshiaki Himemoto. 2025-04-09. Hunting axion dark matter signatures in low-frequency terrestrial magnetic fields. https://arxiv.org/abs/2504.06653

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