Ken‐Ichi Nishikawa
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View article: Synthetic spectra from particle-in-cell simulations of relativistic jets containing an initial toroidal magnetic field
Synthetic spectra from particle-in-cell simulations of relativistic jets containing an initial toroidal magnetic field Open
The properties of relativistic jets, their interaction with the environment, and their emission of radiation can be self-consistently studied by using collisionless particle-in-cell (PIC) numerical simulations. Using three-dimensional rela…
View article: <tt>R-JET:</tt> A Postprocessing Code for Radiative Transport in Relativistic Jets
R-JET: A Postprocessing Code for Radiative Transport in Relativistic Jets Open
We describe a postprocessing radiative transport code for computing the spectra, the core shift, and the surface-brightness distribution of special relativistic jets with arbitrary optical thickness. The jet consists of an electron–positro…
View article: R-JET: A postprocessing code for radiative transport in relativistic jets
R-JET: A postprocessing code for radiative transport in relativistic jets Open
We describe a post-processing radiative transport code for computing the spectra, the coreshift, and the surface-brightness distribution of special relativistic jets with arbitrary optical thickness. The jet consists of an electron-positro…
View article: Synthetic Spectra from Particle-in-cell Simulations of Relativistic Jets containing an initial Toroidal Magnetic Field
Synthetic Spectra from Particle-in-cell Simulations of Relativistic Jets containing an initial Toroidal Magnetic Field Open
The properties of relativistic jets, their interaction with the environment, and their emission of radiation can be self-consistently studied by using collisionless particle-in-cell (PIC) numerical simulations. Using three-dimensional (3D)…
View article: Formation of Limb-brightened Radio Jets by Angle-dependent Energy Extraction from Rapidly Rotating Black Holes
Formation of Limb-brightened Radio Jets by Angle-dependent Energy Extraction from Rapidly Rotating Black Holes Open
Using general relativistic magnetohydrodynamic simulations, it has been suggested that the rotational energy of a rapidly rotating black hole (BH) is preferentially extracted along the magnetic field lines threading the event horizon in th…
View article: Formation of limb-brightened radio jets by angle-dependent energy extraction from rapidly rotating black holes
Formation of limb-brightened radio jets by angle-dependent energy extraction from rapidly rotating black holes Open
By general relativistic magnetohydrodynamic simulations, it is suggested that the rotational energy of a rapidly rotating black hole (BH) is preferentially extracted along the magnetic field lines threading the event horizon in the middle …
View article: Two-dimensional Particle-in-cell Simulations of Axisymmetric Black Hole Magnetospheres: Angular Dependence of the Blandford–Znajek Flux
Two-dimensional Particle-in-cell Simulations of Axisymmetric Black Hole Magnetospheres: Angular Dependence of the Blandford–Znajek Flux Open
We examine the temporary evolution of axisymmetric magnetospheres around rapidly rotating black holes (BHs), by applying our two-dimensional particle-in-cell simulation code. Assuming a stellar-mass BH, we find that the created pairs fail …
View article: Femtosecond laser-induced sub-wavelength plasma inside dielectrics. III. Terahertz radiation emission
Femtosecond laser-induced sub-wavelength plasma inside dielectrics. III. Terahertz radiation emission Open
Electromagnetic radiation within the terahertz (THz) frequency range is of great interest for applications in remote sensing and time-domain spectroscopy. The laser-induced plasmas are promising mediums for generating THz radiation. It has…
View article: 3D PIC Simulations for relativistic jets with a toroidal magnetic field
3D PIC Simulations for relativistic jets with a toroidal magnetic field Open
We have investigated how kinetic instabilities such as the Weibel instability (WI), the mushroom instability (MI), and the kinetic Kelvin–Helmholtz instability (kKHI) are excited in jets without and with a toroidal magnetic field, and how …
View article: Two-dimensional Particle-in-Cell simulations of axisymmetric black hole magnetospheres: angular dependence of the Blandford-Znajek flux
Two-dimensional Particle-in-Cell simulations of axisymmetric black hole magnetospheres: angular dependence of the Blandford-Znajek flux Open
We examine the temporary evolution of axisymmetric magnetospheres around rapidly rotating black holes (BHs), by applying our two-dimensional particle-in-cell simulation code. Assuming a stellar-mass BH, we find that the created pairs fail …
View article: 3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field
3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field Open
Particle-in-Cell simulations can provide a possible answer to an important key issue for astrophysical plasma jets; namely on how a toroidal magnetic field affects the evolution of pair and electron-ion jets. We show that Weibel, mushroom,…
View article: Particle-in-Cell Simulations of Astrophysical Relativistic Jets
Particle-in-Cell Simulations of Astrophysical Relativistic Jets Open
Astrophysical relativistic jets in active galactic nuclei, gamma-ray bursts, and pulsars is the main key subject of study in the field of high-energy astrophysics, especially regarding the jet interaction with the interstellar or intergala…
View article: From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations
From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations Open
Context. Despite decades of dedicated observation and study, the underlying plasma composition of relativistic extragalactic jets remains largely unknown. Aims. Relativistic magnetohydrodynamic (RMHD) models are able to reproduce many of t…
View article: From electrons to Janskys: Full stokes polarized radiative transfer in\n 3D relativistic particle-in-cell jet simulations
From electrons to Janskys: Full stokes polarized radiative transfer in\n 3D relativistic particle-in-cell jet simulations Open
The underlying plasma composition of relativistic extragalactic jets remains\nlargely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to\nreproduce many of the observed macroscopic features of these outflows. The\nnontherm…
View article: PIC methods in astrophysics: PIC simulations of relativistic jets
PIC methods in astrophysics: PIC simulations of relativistic jets Open
The Particle-In-Cell (PIC) method has been developed by Oscar Buneman, Charles Birdsall, Roger W. Hockney, and John Dawson in the 1950s and, with the advances of computing power, has been further developed for several fields such as astrop…
View article: The Emission of Terrestrial Gamma Ray Flashes From Encountering Streamer Coronae Associated to the Breakdown of Lightning Leaders
The Emission of Terrestrial Gamma Ray Flashes From Encountering Streamer Coronae Associated to the Breakdown of Lightning Leaders Open
Terrestrial gamma ray flashes (TGFs) are beams of high‐energy photons associated to lightning. These photons are the bremsstrahlung of energetic electrons whose origin is currently explained by two mechanisms: energizing electrons in weak,…
View article: 3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field
3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field Open
We have investigated how kinetic instabilities such as the Weibel instability (WI), the mushroom instability (MI), and the kinetic Kelvin-Helmholtz instability (kKHI) are excited in jets without and with a toroidal magnetic field, and how …
View article: Rapid particle acceleration due to recollimation shocks and turbulent magnetic fields in injected jets with helical magnetic fields
Rapid particle acceleration due to recollimation shocks and turbulent magnetic fields in injected jets with helical magnetic fields Open
One of the key questions in the study of relativistic jets is how magnetic reconnection occurs and whether it can effectively accelerate electrons in the jet. We performed 3D particle-in-cell (PIC) simulations of a relativistic electron–pr…
View article: The emission of energetic electrons from the complex streamer corona adjacent to leader stepping
The emission of energetic electrons from the complex streamer corona adjacent to leader stepping Open
We here propose to model the production of energetic electrons serving as a source of x-rays and γ -rays, associated to electric discharges in preionized and perturbed air. During its stepping, the leader tip is accompanied by a corona con…
View article: Rapid Particle Acceleration due to Re-collimation in Injected Jets with Helical Magnetic Fields
Rapid Particle Acceleration due to Re-collimation in Injected Jets with Helical Magnetic Fields Open
One of the key open questions in the study of relativistic jets is how magnetic reconnection occurs and whether it can effectively accelerate the jet's electrons. We investigate the evolution of an electron-proton relativistic jet containi…
View article: Relativistic Jet Simulations of the Weibel Instability in the Slab Model to Cylindrical Jets with Helical Magnetic Fields
Relativistic Jet Simulations of the Weibel Instability in the Slab Model to Cylindrical Jets with Helical Magnetic Fields Open
The particle-in-cell (PIC) method was developed to investigate microscopic phenomena, and with the advances in computing power, newly developed codes have been used for several fields, such as astrophysical, magnetospheric, and solar plasm…
View article: Relativistic Jet Simulations of the Weibel Instability in the Slab Model to Cylindrical Jets with Helical Magnetic Fields
Relativistic Jet Simulations of the Weibel Instability in the Slab Model to Cylindrical Jets with Helical Magnetic Fields Open
The Particle-In-Cell (PIC) method has been developed in order to investigate microscopic phenomena, and with the advances of computing power, newly developed codes have been used for several fields such as astrophysical, magnetospheric, an…
View article: Relativistic Jet Simulations of the Weibel Instability in the Slab Model to Cylindrical Jets with Helical Magnetic Fields
Relativistic Jet Simulations of the Weibel Instability in the Slab Model to Cylindrical Jets with Helical Magnetic Fields Open
The Particle-In-Cell (PIC) method has been developed in order to investigate microscopic phenomena, and with the advances of computing power, newly developed codes have been used for several fields such as astrophysical, magnetospheric, an…
View article: Identifying 3‐D Vortex Structures At/Around the Magnetopause Using a Tetrahedral Satellite Configuration
Identifying 3‐D Vortex Structures At/Around the Magnetopause Using a Tetrahedral Satellite Configuration Open
Identifying vortices is the key to understanding the turbulence in plasma shear layers. This paper aims to provide general guidelines for identifying 3‐D vortex structures. Currently, no single precise definition of a vortex is universally…
View article: Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields: Dependence on Jet Radius
Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields: Dependence on Jet Radius Open
In this study, we investigate the interaction of jets with their environment at a microscopic level, which is a key open question in the study of relativistic jets. Using small simulation systems during past research, we initially studied …
View article: Magnetic Dissipation in Relativistic Jets
Magnetic Dissipation in Relativistic Jets Open
The most promising mechanisms for producing and accelerating relativistic jets, and maintaining collimated structure of relativistic jets involve magnetohydrodynamical (MHD) processes. We have investigated the magnetic dissipation mechanis…
View article: Observations of Transient ISS Floating Potential Variations during High Voltage Solar Array Operations
Observations of Transient ISS Floating Potential Variations during High Voltage Solar Array Operations Open
The International Space Station (ISS) continues to be a world-class space research laboratory after over 15 years of operations, and it has proven to be a fantastic resource for observing spacecraft floating potential variations related to…
View article: Pick-up Ion Scattering in the Outer Heliosheath - implications for IBEX and Voyager 1 observations.
Pick-up Ion Scattering in the Outer Heliosheath - implications for IBEX and Voyager 1 observations. Open
The nearly circular band of energetic neutral atom (ENA) emission dominating the field of view of the Interplanetary Boundary EXplorer satellite (IBEX), is most commonly attributed to the effect of charge exchange of secondary pick-up ions…