Constraining the photon mass via Schumann resonances

TL;DR

This paper uses Earth's Schumann resonances to set a more stringent upper limit on the photon mass, improving previous bounds by considering realistic atmospheric conductivity profiles.

Contribution

It introduces a novel method to constrain photon mass using Schumann resonances and updates previous limits with more realistic atmospheric models.

Findings

New upper bound on photon mass: 2.5 x 10^{-14} eV/c^2

Improved sensitivity over previous limits by a factor of 9.6

Utilizes Earth's natural electromagnetic resonances for fundamental physics constraints

Abstract

The photon is the paradigm for a massless particle and current experimental tests set severe upper bounds on its mass. Probing such a small mass, or equivalently large Compton wavelength, is challenging at laboratory scales, but planetary or astrophysical phenomena may potentially reach much better sensitivities. In this work we consider the effect of a finite photon mass on Schumann resonances in the Earth-ionosphere cavity, since the TM modes circulating Earth have eigen-frequencies of order $\mathcal{O} (10 \, {\rm Hz})$ that could be sensitive to $m_\gamma \approx 10^{-14} \, {\rm eV/c}^2$. In particular, we update the limit from Kroll [Phys. Rev. Lett. 27, 340 (1971)], $m_\gamma \leq 2.4 \times 10^{-13} \, {\rm eV/c}^2$, by considering realistic conductivity profiles for the atmosphere. We find the conservative upper bound $m_\gamma \leq 2.5 \times 10^{-14} \, {\rm eV/c}^2$, a factor 9.6 more strict than Kroll's earlier projection.