Crustal Quakes Spark Magnetospheric Blasts: Imprints of Realistic Magnetar Crust Oscillations on the Fast Radio Burst Signal

Abstract

Many transients believed to originate from magnetars are thought to be triggered by crustal activity, which feeds back on the surrounding magnetosphere. These perturbations, through a variety of proposed mechanisms, can convert a fraction of the magnetic energy stored in the magnetosphere, as well as the energy injected by crustal activity itself into electromagnetic emission, including X-ray bursts and fast radio bursts. Here we provide a first glimpse of this process by coupling magneto-elastic dynamics simulations of the crust to fully three-dimensional relativistic resistive force-free electrodynamic simulations of the magnetosphere. Our simulations demonstrate that the elastodynamical motions of the surface launch a series of fast magnetosonic and Alfv\'en waves into the magnetosphere. These waves rapidly enter a nonlinear regime, ultimately giving rise to a wide range of phenomena, including monster shock formation, relativistic blast waves, trapped Alfv\'en waves, nonlinear Alfv\'en wave ejecta, and transient equatorial current sheets interacting with these waves. After the initial nonlinear phase, the magnetosphere is partially combed out, resembling a strongly perturbed split monopole configuration. Our results can offer hints and potential constraints on fast radio burst emission mechanisms, in particular for hyperactive repeating sources, by placing tight bounds on energy conversion efficiency, and possible quasi-periodic imprints on magnetospheric waves by elastic oscillations of the crust.