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Accreting neutron stars are one of the main targets for continuousgravitational wave searches, as asymmetric accretion may lead to quadrupolardeformations, or `mountains', on the crust of the star, which sourcegravitational wave emission at twice the rotation frequency. The gravitationalwave torque may also impact on the spin evolution of the star, possiblydictating the currently observed spin periods of neutron stars in Low MassX-ray Binaries and leading to the increased spindown rate observed duringaccretion in PSR J1023+0038. Previous studies have shown that deformed reactionlayers in the crust of the neutron star lead to thermal and compositionalgradients that can lead to gravitational wave emission. However, there are norealistic constraints on the level of asymmetry that is expected. In this paperwe consider a natural source of asymmetry, namely the magnetic field, andcalculate the density and pressure perturbations that are expected in the crustof accreting neutron stars. In general we find that only the outermost reactionlayers of the neutron star are strongly perturbed. The mass quadrupole that weestimate is generally small and cannot explain the increase of spin-down rateof PSR J1023+0038. However, if strong shallow heating sources are present atlow densities in the crust, as cooling observations suggest, these layers willbe strongly perturbed and the resulting quadrupole could explain the observedspindown of PSR J1023+0038, and lead to observable gravitational wave signalsfrom systems with higher accretion rates.

Asymmetric accretion and thermal `mountains' in magnetized neutron star crusts