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.
@article{arxiv.1802.00885,
title = {Measurement and subtraction of Schumann resonances at gravitational-wave interferometers},
author = {Michael W. Coughlin and Alessio Cirone and Patrick Meyers and Sho Atsuta and Valerio Boschi and Andrea Chincarini and Nelson L. Christensen and Rosario De Rosa and Anamaria Effler and Irene Fiori and Mark Golkowski and Melissa Guidry and Jan Harms and Kazuhiro Hayama and Yuu Kataoka and Jerzy Kubisz and Andrzej Kulak and Michael Laxen and Andrew Matas and Janusz Mlynarczyk and Tsutomu Ogawa and Federico Paoletti and Jacobo Salvador and Robert Schofield and Kentaro Somiya and Eric Thrane},
journal= {arXiv preprint arXiv:1802.00885},
year = {2018}
}