Searching for Ultralight Dark Matter Conversion in Solar Corona using Low Frequency Array Data

TL;DR

This paper reports a search for ultralight dark matter converting into radio signals in the solar corona using LOFAR data, setting new constraints on dark photon and axion couplings.

Contribution

First search for monochromatic radio signals from dark matter conversion in the solar corona using LOFAR, establishing improved upper limits on dark photon and axion couplings.

Findings

Set upper limit on dark photon-photon kinetic mixing as low as 10^{-13}

Derived upper limit on axion-photon coupling better than Light-Shining-through-a-Wall experiments

Improved constraints over previous cosmic microwave background bounds

Abstract

Ultralight dark photons and axions are well-motivated hypothetical dark matter candidates. Both dark photon dark matter and axion dark matter can resonantly convert into electromagnetic waves in the solar corona when their mass is equal to the solar plasma frequency. The resultant electromagnetic waves appear as monochromatic signals within the radio-frequency range with an energy equal to the dark matter mass, which can be detected via radio telescopes for solar observations. Here we show our search for converted monochromatic signals in the observational data collected by the high-sensitivity Low Frequency Array (LOFAR) telescope and establish an upper limit on the kinetic mixing coupling between dark photon dark matter and photon, which can reach values as low as $10^{-13}$ within the frequency range of $30-80$ MHz. This limit represents an improvement of approximately one order of magnitude better than the existing constraint from the cosmic microwave background observation. Additionally, we derive an upper limit on the axion-photon coupling within the same frequency range, which is better than the constraints from Light-Shining-through-a-Wall experiments while not exceeding the CERN Axion Solar Telescope (CAST) experiment or other astrophysical bounds.