Resonant Conversion of Wave Dark Matter in the Ionosphere

TL;DR

This paper explores how wave-like dark matter can convert into low-frequency radio waves in the Earth's ionosphere through resonance, proposing a new detection method sensitive to specific dark matter mass ranges.

Contribution

It introduces a novel approach to detect dark matter via resonant conversion in the ionosphere, solving a boundary-value problem to model the process accurately.

Findings

Resonant conversion occurs at dark matter masses around 10^{-9} to 10^{-8} eV.

A small dipole antenna can significantly enhance detection sensitivity.

The method opens new parameter space for dark matter searches.

Abstract

We consider resonant wave-like dark matter conversion into low-frequency radio waves in the Earth's ionosphere. Resonant conversion occurs when the dark matter mass and the plasma frequency coincide, defining a range $m_{ \text{DM} } \sim 10^{-9} - 10^{-8}$ eV where this approach is best suited. Owing to the non-relativistic nature of dark matter and the typical variational scale of the Earth's ionosphere, the standard linearized approach to computing dark matter conversion is not suitable. We therefore solve a second-order boundary-value problem, effectively framing the ionosphere as a driven cavity filled with a positionally-varying plasma. An electrically-small dipole antenna targeting the generated radio waves can be orders of magnitude more sensitive to dark photon and axion-like particle dark matter in the relevant mass range. The present study opens up a promising way of testing hitherto unexplored parameter space which could be further improved with a dedicated instrument.