  The migration of planetary cores embedded in a protoplanetary disk is an
important mechanism within planet-formation theory, relevant for the
architecture of planetary systems. Consequently, planet migration is actively
discussed, yet often results of independent theoretical or numerical studies
are unconstrained due to the lack of observational diagnostics designed in
light of planet migration. In this work we follow the idea of inferring the
migration behavior of embedded planets by means of the characteristic radial
structures that they imprint in the disk's dust density distribution. We run
hydrodynamical multifluid simulations of gas and several dust species in a
locally isothermal $\alpha$-disk in the low-viscosity regime ($\alpha=10^{-5}$)
and investigate the obtained dust structures. In this framework, a planet of
roughly Neptune mass can create three (or more) rings in which dust
accumulates. We find that the relative spacing of these rings depends on the
planet's migration speed and direction. By performing subsequent radiative
transfer calculations and image synthesis we show that - always under the
condition of a near-inviscid disk - different migration scenarios are, in
principle, distinguishable by long-baseline, state-of-the-art ALMA
observations.
