Force-free magnetosphere on near-horizon geometry of near-extreme Kerr black holes

Understand

We study force-free magnetospheres in the Blandford-Znajek process from rapidly rotating black holes by adopting the near-horizon geometry of near-extreme Kerr black holes (near-NHEK).

• It is shown that the Znajek regularity condition on the horizon can be directly derived from the resulting stream equation.
• In terms of the condition, we split the full stream equation into two separate equations.
• Approximate solutions around the rotation axis are derived.