Limits on High-Frequency Gravitational Waves in Planetary Magnetospheres

TL;DR

This paper explores the potential of planetary magnetospheres, like Earth's and Jupiter's, to detect high-frequency gravitational waves by converting them into photons, presenting initial limits and future sensitivities.

Contribution

It introduces a novel method of using planetary magnetospheres as natural laboratories for HFGW detection and provides the first observational limits from satellite data.

Findings

Existing satellite data set new limits on HFGWs in certain frequency bands.

Juno mission data offers the first constraints on HFGWs near Jupiter.

Future dedicated observations could significantly improve detection sensitivity.

Abstract

High-frequency gravitational waves (HFGWs) carry a wealth of information on the early Universe with a tiny comoving horizon and astronomical objects of small scale but with dense energy. We demonstrate that the nearby planets, such as Earth and Jupiter, can be utilized as a laboratory for detecting the HFGWs. These GWs are then expected to convert to signal photons in the planetary magnetosphere, across the frequency band of astronomical observation. As a proof of concept, we present the first limits from the existing low-Earth-orbit satellite for specific frequency bands and project the sensitivities for the future more-dedicated detections. The first limits from Juno, the latest mission orbiting Jupiter, are also presented. Attributed to the long path of effective GW-photon conversion and the wide angular distribution of signal flux, we find that these limits are highly encouraging, for a broad frequency range including a large portion unexplored before.