Seminars IFIC

#Student Seminar: Magnetospheric electrodynamics: Studying the Blandford/Znajek process in GR time evolution simulations of force-free electrodynamics around Kerr black holes

by Mr. Jens Mahlmann (Departamento de Astronomía y Astrofísica, U. Valencia)

Monday, 13 November 2017 from to (Europe/Madrid)
at Campus Burjassot ( Salón de grados, Facultad de Física )
In continuation of the development and implementation of numerical methods to solve the relativistic Grad-Shafranov equation (Blandford and Znajek, 1977; Uzdensky, 2005; Contopoulos et al., 2013) in order to obtain accurate initial data for magnetospheric field configurations we present our recent progress in implementing a time evolution scheme for general relativistic force-free electrodynamics (as found in, e.g., Komissarov, 2004, 2007; Etienne et al., 2017) within the frameworks of the Einstein Toolkit. We observe that the evolution of magnetic field configurations which are likely to show an observable impact of the Blandford/Znajek process (e.g., split-monopole or paraboloidally shaped configurations) yields additional challenges on a spacetime without excisions, especially in guaranteeing the divergence-free condition, and, in sustaining current sheets over significant timescales. We therefore suggest the implementation of an augmented system of evolution equations including a general relativistic divergence cleaning which is able to limit both dissipation and advection of divB (cf. Mignone and Tzeferacos, 2010). Furthermore, we consider recent works like Parfrey et al. (2017) as promising strategies to resolve current sheets over timescales allowing reliable studies of the Blandford/Znajek process. A general introduction into the features of the presented force-free evolution equations is supplemented by a presentation of preliminary results of time evolutions of field configurations (split-monopole and paraboloidal solutions to the Grad-Shafranov equation) and their possible feedback to a dynamical metric.