  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.
