Magnetic-induced force noise in LISA Pathfinder free-falling test masses

TL;DR

This paper estimates the magnetic-induced force noise in LISA Pathfinder's test masses, crucial for gravitational wave detection, providing measurements and discussing effects of space weather on noise levels.

Contribution

It presents the first complete estimate of magnetic-induced acceleration noise in LISA Pathfinder, including effects of space weather on noise variability.

Findings

Magnetic-induced acceleration noise at 1 mHz is approximately 0.25 fm/s^2/√Hz.

At 0.1 mHz, the noise is about 1.01 fm/s^2/√Hz.

Non-stationarities in interplanetary magnetic fields can influence noise during space weather events.

Abstract

LISA Pathfinder was a mission designed to test key technologies required for gravitational wave detection in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime, which corresponds to the measurement band of interest for future space-borne gravitational wave observatories. Magnetic-induced forces couple to the test mass motion, introducing a contribution to the relative acceleration noise between the free falling test masses. In this Letter we present the first complete estimate of this term of the instrument performance model. Our results set the magnetic-induced acceleration noise during the February 2017 noise run of $\rm 0.25_{-0.08}^{+0.15}\,fm\,s^{-2}/\sqrt{Hz}$ at 1 mHz and $\rm 1.01_{-0.24}^{+0.73}\, fm\,s^{-2}/\sqrt{Hz}$ at 0.1 mHz. We also discuss how the non-stationarities of the interplanetary magnetic field can affect these values during extreme space weather conditions.