Observable Emission Features of Black Hole GRMHD Jets on Event Horizon Scales

The general-relativistic magnetohydrodynamical (GRMHD) formulation for black hole-powered jets naturally gives rise to a stagnation surface, wherefrom inflows and outflows along magnetic field lines that thread the black hole event horizon originate. We derive a conservative formulation for the transport of energetic electrons which are initially injected at the stagnation surface and subsequently transported along flow streamlines. With this formulation the energy spectra evolution of the electrons along the flow in the presence of radiative and adiabatic cooling is determined. For flows regulated by synchrotron radiative losses and adiabatic cooling, the effective radio emission region is found to be finite, and geometrically it is more extended along the jet central axis. Moreover, the emission from regions adjacent to the stagnation surface is expected to be the most luminous as this is where the freshly injected energetic electrons concentrate. An observable stagnation surface is thus a strong prediction of the GRMHD jet model with the prescribed non-thermal electron injection. Future millimeter/sub-millimeter (mm/sub-mm) very-long-baseline interferometric (VLBI) observations of supermassive black hole candidates, such as the one at the center of M87, can verify this GRMHD jet model and its associated non-thermal electron injection mechanism.Comment: 19 pages, 12 figure; accepted for publication in Ap

Steady General Relativistic Magnetohydrodynamic Inflow/Outflow Solution along Large-Scale Magnetic Fields that Thread a Rotating Black Hole

General relativistic magnetohydrodynamic (GRMHD) flows along magnetic fields threading a black hole can be divided into inflow and outflow parts, according to the result of the competition between the black hole gravity and magneto-centrifugal forces along the field line. Here we present the first self-consistent, semi-analytical solution for a cold, Poynting flux-dominated (PFD) GRMHD flow, which passes all four critical (inner and outer, Alfven and fast magnetosonic) points along a parabolic streamline. By assuming that the dominating (electromagnetic) component of the energy flux per flux tube is conserved at the surface where the inflow and outflow are separated, the outflow part of the solution can be constrained by the inflow part. The semi-analytical method can provide fiducial and complementary solutions for GRMHD simulations around the rotating black hole, given that the black hole spin, global streamline, and magnetizaion (i.e., a mass loading at the inflow/outflow separation) are prescribed. For reference, we demonstrate a self-consistent result with the work by McKinney in a quantitative level.Comment: 13 Pages, incliding 2 tables and 5 Figures; accepted by Ap

Fabrication of micro-structured surface of plants-derived polyamide using femtosecond laser and their frictional properties

For the purpose of developing the new polymeric tribomaterials using biopolymer, the fabrication of micro-structured surfaces of plants-derived polyamide (PA) using femtosecond laser and their frictional properties were investigated. In this study, the effect of processing parameter such as laser power, laser speed and pitch distance on the fabrication of micro-structured surfaces of polyamide 66 (PA66) and plants-derived polyamide 1010 (PA1010) was investigated experimentally, and their frictional properties and wettability were evaluated. Polyamides (PA1010 and PA66) were extruded by a twin screw extruder and injection-molded to 30mm × 30mm × 3mm sheet. The micro-structured surfaces on the polyamides were fabricated by femtosecond laser. The micro-structured surfaces on the polyamides by laser fabrication were observed by laser microscope and scanning electron microscope (SEM). Frictional properties were measured by a ball on plate reciprocating type sliding wear tester under lubrication conditions. It was found that the surface microchannels are able to be fabricated by the femtosecond laser and have a good effect for the improvement of the frictional properties and wettability of PA66 and plants-derived PA1010. Laser power influences strongly on the microchannels size, wettability and frictional properties. This may be attributed that the micro-structured surface plays an important role in the key components for the polymeric tribomaterials. © 2016 Author(s).MEXT, Ministry of Education, Culture, Sports, Science, and Technolog