2022-03-18 Abstract
Title: Activity of black hole magnetospheres: formation of limb-brightened jets from low accreting systems
Speaker: Kouchi Hirotani
Date: Mar 11 at 14:30
Location: R124, Physics Building
Abstract:
We examine the temporary evolution of axisymmetric magnetospheres around rapidly rotating black holes (BHs), applying my two-dimensional particle-in-cell simulation code. By virtue of the formation of a return current toward the equator within the ergosphere, the BH's rotational energy is extracted electromagnetically via the Blandford-Znajek process. Provided that the mass accretion rate is much small compared to the Eddington rate, it is found that the extracted energy flux modulates slowly due to magnetic reconnections, and that the flux concentrates along the magnetic field lines threading the horizon in the middle latitudes. Assuming that the kinetic energy flux of a jet is proportional to this Poynting flux, we demonstrate that the synchrotron emissivity peaks at a certain distance from the jet axis, which appears limb-brightened when we observe the jet at moderate viewing angles. We discuss its implications on the VLBI observations of M87 and other several active galactic nuclei.