Constraints on force-free magnetospheres for Kerr(-AdS) black holes with non-null currents

Understand

Force-free magnetospheres are of particular interest due to their role in energy extraction from Kerr black holes via the Blandford-Znajek process.

• Recently, a class of exact analytic solutions has been found with null currents [1,2].
• In this paper, we elaborate some constraints on various force-free magnetosphere solutions with non-null currents, utilizing the Newman-Penrose electromagnetic scalars to categorize a range of different cases.
• We perform a thorough search for stationary and axisymmetric (SAS) solutions, and find that putative SAS solutions within the categories considered generically exhibit singularities on the horizon.