Hunting axion dark matter signatures in terrestrial magnetic fields

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概要

Axions are one of the candidates for the unknown dark matter. Ultralight axions form a huge number of clouds in galactic halos. When such an axion cloud passes through the Earth, it interacts electromagnetically with the geomagnetic field and generates a monochromatic electromagnetic wave whose frequency corresponding to the axion mass. Recently we modeled the axion-induced electromagnetic wave signals by solving Maxwell’s equations under the appropriate boundary conditions of the ionosphere for geomagnetic fields and showed that Earth’s natural environment can serve as a powerful probe for ultralight axion dark matter with masses ranging from 10^{-15} eV — 10^{-13} eV. Based on the derived theoretical model, we searched for axion-induced magnetic field signals within the observational data of global geomagnetic field variations (Eskdalemuir Observatory, 2012–2022). In this talk, I report on the idea of the search, the data analysis mehtod, the results of the search having several tens of axion signal candidates.