Measurement and subtraction of Schumann resonances at gravitational-wave interferometers

TL;DR

This paper demonstrates the use of dedicated magnetometer measurements at gravitational-wave detector sites to effectively reduce Schumann resonance-induced correlated magnetic noise, improving the detection of stochastic gravitational-wave backgrounds.

Contribution

It presents the first results of magnetic noise subtraction using data from gravitational-wave detector sites, enhancing noise mitigation strategies for gravitational-wave observations.

Findings

Dedicated magnetometer measurements can reduce coherence to uncorrelated noise levels.

Magnetometers should be placed at least one meter apart to avoid mutual attraction effects.

Comparison with a network of permanent stations shows improved noise subtraction.

Abstract

Correlated magnetic noise from Schumann resonances threatens to contaminate the observation of a stochastic gravitational-wave background in interferometric detectors. In previous work, we reported on the first effort to eliminate global correlated noise from the Schumann resonances using Wiener filtering, demonstrating as much as a factor of two reduction in the coherence between magnetometers on different continents. In this work, we present results from dedicated magnetometer measurements at the Virgo and KAGRA sites, which are the first results for subtraction using data from gravitational-wave detector sites. We compare these measurements to a growing network of permanent magnetometer stations, including at the LIGO sites. We show how dedicated measurements can reduce coherence to a level consistent with uncorrelated noise. We also show the effect of mutual magnetometer attraction, arguing that magnetometers should be placed at least one meter from one another.