Low-frequency radio telescopes sensitivity to light dark matter

TL;DR

The paper develops a framework for resonant DM–photon conversion in solar-system plasmas and quantifies how space-based, low-frequency radio instruments can probe light DM candidates (ALPs and DPs) through signals from the Sun, Jupiter, and the Earth. It derives the conversion probability and connects it to an observable DM-induced flux density, incorporating realistic plasma, magnetic-field models, and environmental/instrumental noise via the radiometer equation. Sensitivity projections for current and planned space-based instruments, including lunar farside arrays, show that DP searches from the Sun and ALP searches from Jupiter can access new regions of parameter space, with the strongest potential realized by future lunar-based observatories. The study highlights the practical importance of distance, array size, and noise modeling, and points to targeted follow-up work with mission-specific analyses to optimize search strategies for light DM.

Abstract

Ground-based radio telescopes are routinely used to search for light dark matter (DM) candidates such as axion-like particles or dark photons. These instruments face however inherent limitations to push the searches to masses below $10^{-7}$ eV, due to the effect of the Earth's ionosphere. The extant and planned space- or Moon-based radio telescopes motivate this study: We systematically investigate their sensitivity to resonant conversion of light DM into radio signals from three solar system targets: the Sun, the Earth, and Jupiter. The perspectives are especially encouraging for dark photon searches using the Sun as a target, and for axion-like particles conversion in Jupiter's magnetosphere.

Figures (10)

• Figure 1: Plasma frequency profiles and inverse logarithmic gradients of $\omega_{\rm pl}^2$ for the Sun, Jupiter, and the Earth, expressed in terms of $\bar{h}=h/H_{\rm eff}$, where the effective heighs are $H_{\rm eff}=R_\odot, H_\oplus, H_J$ in the three cases.
• Figure 2: Transverse magnetic field profiles $|\mathbf{B}_T|$ for the Sun, Jupiter, and the Earth, in units normalised as in Fig \ref{['fig:omega_pl_targets']}. In the adopted solar model, the value of the transverse field changes sign around $\bar{h}\simeq 0.7$.
• Figure 3: DM ALP line strength maps for the three targets: the Earth, Jupiter and the Sun, from left to right.
• Figure 4: DM DP line strength maps for the three targets: the Earth, Jupiter and the Sun, from left to right.
• Figure 5: Sensitivity to DM ALP (left) and DP (right) radio lines from the Sun, for sky-dominated analyses (Galactic background plus QTN at 1 AU) and for different observation distances (colour bar). The DP curves exhibit a clear turnover around $m_a\!\sim\!10^{-9}\,\mathrm{eV}$, corresponding to the mass below which the QTN contribution exceeds the Galactic background.