Resonant axion-plasmon conversion in neutron star magnetospheres

TL;DR

This paper investigates how resonant axion-plasmon conversion in neutron star magnetospheres affects axion detection via radio signals, revealing that it can significantly reduce expected signals and alter experimental constraints.

Contribution

It introduces a novel resonant conversion mechanism analogous to the neutrino MSW effect, showing its impact on axion-photon conversion signals and experimental sensitivities.

Findings

Resonant conversion can cause nonradiative power loss, reducing photon flux.

Radio telescope sensitivities may be overestimated if plasmon effects are neglected.

Experimental constraints need reassessment considering this resonant conversion mechanism.

Abstract

Resonant axion-plasmon conversion in the magnetospheres of magnetars may substantially impact the landscape of dark-matter axion detection. This work explores how resonant axion-plasmon conversion, through a mechanism that is analogous to the Mikheyev-Smirnov-Wolfenstein (NSW) effect in neutrinos, modify the expected radio signals from axion-photon conversions observed on Earth. Critically, the resonant conversion radius lies within the region expected for axion-photon conversion, introducing a nonradiative power loss that diminishes the anticipated photon flux. Our analysis demonstrates that this effect can reduce radio telescope sensitivities, shifting them into regions excluded by previous experiments. These findings compel a reassessment of experimental constraints derived from radio signatures of axion-photon conversions and highlight the necessity of accounting for plasmon effects in astrophysical axion searches. The presented corrections provide critical insights for refining the detection strategies of future telescope-based dark matter axion experiments.