Jan 13 – 16, 2020
IFPU, Miramare campus, Trieste, Italy
Europe/Rome timezone

Force-free electrodynamics near rotation axis of a Kerr black hole

Jan 14, 2020, 3:00 PM
15m
IFPU, Miramare campus, Trieste, Italy

IFPU, Miramare campus, Trieste, Italy

Via Beirut 2, Trieste, Italy

Speaker

Troels Harmark (Niels Bohr Institute)

Description

Despite their potential importance for understanding astrophysical jets, physically realistic exact solutions for magnetospheres around Kerr black holes have not been found, even in the force-free approximation. Instead approximate analytical solutions such as the Blandford-Znajek (split-)monopole, as well as numerical solutions, have been constructed. In this talk we consider a new approach to the analysis and construction of such magnetospheres. We consider force-free electrodynamics close to the rotation axis of a magnetosphere surrounding a Kerr black hole assuming axisymmetry. This is the region where the force-free approximation should work the best, and where the jets are located. We perform a systematic study of the asymptotic region with (split-)monopole, paraboloidal and vertical asymptotic behaviors. Imposing asymptotics similar to a (split-)monopole, we find that demanding regularity at the rotation axis and the event horizon restricts solutions of the stream equation so much that it is not possible for a solution to be continuously connected to the static (split-)monopole around the Schwarzschild black hole in the limit where the rotation goes to zero. This provides independent evidence to the issues discovered with the asymptotics of the Blandford-Znajek (split-)monopole in Ref. [1] from which it follows that its perturbative construction is inconsistent.

Primary author

Troels Harmark (Niels Bohr Institute)

Presentation materials