Impact of Schumann resonances on the Einstein Telescope and projections for the magnetic coupling function

TL;DR

This paper assesses how Schumann resonances and local magnetic noise could affect the Einstein Telescope's sensitivity, providing forecasts and limits on magnetic coupling to ensure optimal gravitational-wave detection.

Contribution

It offers the first detailed forecast of magnetic noise impact on the Einstein Telescope and sets upper limits on magnetic coupling functions for future detector design.

Findings

Magnetic contamination could limit Einstein Telescope sensitivity if not properly mitigated.

Magnetic coupling must be 100 to 10,000 times better than current LIGO/Virgo levels below 30 Hz.

Local and global magnetic effects require targeted shielding to preserve detector performance.

Abstract

Correlated magnetic noise in the form of Schumann resonances could introduce limitations to the gravitational-wave background searches of future Earth-based gravitational-wave detectors. We consider recorded magnetic activity at a candidate site for the Einstein Telescope, and forecast the necessary measures to ensure that magnetic contamination will not pose a threat to the science goals of this third-generation detector. In addition to global magnetic effects, we study local magnetic noise and the impact it might have on co-located interferometers. We express our results as upper limits on the coupling function of magnetic fields to the interferometer arms, implying that any larger values of magnetic coupling into the strain channel would lead to a reduction in the detectors' sensitivity. For gravitational-wave background searches below $\sim 30$ Hz it will be necessary for the Einstein Telescope magnetic isolation coupling to be two to four orders of magnitude better than that measured in the current Advanced LIGO and Virgo detectors.