Radiation from accelerated particles in relativistic jets with shocks, shear-flow, and reconnection

Abstract

Abstract. We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma for electron-positron and electron-ion plasmas. Strong magnetic fields generated in the trailing jet shock lead to transverse deflection and acceleration of the electrons. We have self-consistently calculated the radiation from the electrons accelerated in the turbulent magnetic fields for different jet Lorentz factors. We find that the synthetic spectra depend on the bulk Lorentz factor of the jet, the jet temperature, and the strength of the magnetic fields generated in the shock. We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic (core) jet and an unmagnetized sheath plasma. We discuss particle acceleration in collimation shocks for AGN jets formed by relativistic MHD simulations. Our calculated spectra should lead to a better understanding of the complex time evolution and/or spectral structure from gamma-ray bursts, relativistic jets, and supernova remnants.

PIC methods in astrophysics: simulations of relativistic jets and kinetic physics in astrophysical systems

“…To date, kKHI and mushroom instability (MI) simulations have been performed in slab (Alves et al 2012;Nishikawa et al 2013b;Alves et al 2015a;Nishikawa et al 2014b;Alves et al 2015b;Liang et al 2013a, b) and in cylindrical geometries (Alves 2010;Nishikawa et al 2014a), but on periodic grids with no shock system. Full scale shock simulations have not incorporated velocity shear interaction with the ambient plasma (interstellar medium) (e.g., Nishikawa et al 2009;Choi et al 2014;Ardaneh et al 2015Ardaneh et al , 2016, and to date only global simulations using a very small simulation system have been performed (Nishikawa et al 2003(Nishikawa et al , 2006a(Nishikawa et al , 2014aNg and Noble 2006). Simulations by Ng and Noble (2006) pointed to the growth of kKHI, but a much larger simulation system is required to study properly both shocks and velocity shear instabilities (kKHI and MI) (e.g., Nishikawa et al 2016a).…”

“…In order to investigate the possible structures of electromagnetic fields in jets including instabilities which are generated due to the velocity-shear, simulations with cylindrical jets need to be performed because relativistic jets and internal filamentary structures are more suitably modeled as intrinsically cylindrical shape (Nishikawa et al 2014a(Nishikawa et al , 2016a. Nishikawa et al (2016a) have performed 3D PIC simulations involving a cylindrical jet injection into an ambient plasma without a magnetic field in order to investigate shocks (Weibel instability) and velocity shear instabilities (kKHI and MI) simultaneously.…”

“…15 Isocontour plots of current density component J x with magnetic field lines (one fifth of the jet size) for a an e À À p þ and b an e AE jet after t ¼ 300x À1 pe . The 3D displays are clipped along the jet and perpendicular to the jet in order to view the interior Image reproduced with permission from Nishikawa et al (2014a); copyright by AAS generated near the velocity shear and the individual current filaments are wrapped by the magnetic field. The clear difference in the magnetic field structure between these two cases may make it possible to distinguish different jet compositions via differences in circular and linear polarization.…”

Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields

“…The RPIC code used in these studies is a modified version of the TRISTAN code [11], parallelized with MPI and utilized for various research projects (e.g., [12][13][14]). To date, RPIC simulations of the kKHI have been performed in slab [15][16][17][18][19][20][21][22][23][24] and cylindrical geometries using periodic boundary conditions [25,26]. Previously, full-scale shock simulations have not incorporated velocity shear interactions at the jet boundary with the ambient plasma (interstellar medium) (e.g., [13]), and global shock simulations including velocity shear interactions performed to date used only very small simulation boxes [27][28][29].…”

Quantitatively consistent computation of coherent and incoherent radiation in particle-in-cell codes—A general form factor formalism for macro-particles

“…Making quantitative predictions on the measurable outcome of these experiments is done by so-called synthetic diagnostics. An essential form of these synthetic diagnostics are predictions on the radiation emissions [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. However, most of these simulations lack quantitative predictions due to the small number of sample particles used (see [22] for details), but also due to an inconsistent treatment of the discrete nature of the electrons represented by macro-particles in PIC codes.…”