Electromagnetic Jets from Stars and Black Holes

TL;DR

This paper develops exact and approximate force-free electromagnetic solutions for jets from stars and black holes, revealing how their properties differ and illustrating key features of the energy extraction process in a simplified model.

Contribution

It provides analytic force-free solutions modeling jets from stars and black holes, highlighting differences in jet structure and energy extraction mechanisms.

Findings

Star jets are surrounded by a current sheet.

Black hole jets are smooth without a current sheet.

Effective resistance calculations compare to circuit models.

Abstract

We present analytic force-free solutions modeling rotating stars and black holes immersed in the magnetic field of a thin disk that terminates at an inner radius. The solutions are exact in flat spacetime and approximate in Kerr spacetime. The compact object produces a conical jet whose properties carry information about its nature. For example, the jet from a star is surrounded by a current sheet, while that of a black hole is smooth. We compute an effective resistance in each case and compare to the canonical values used in circuit models of energy extraction. These solutions illustrate all of the basic features of the Blandford-Znajek process for energy extraction and jet formation in a clean setting.