Kazumi Nishimura - LANL

Kazumi Nishimura
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Kazumi Nishimura

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Astrophysics (5)

Publications Authored By Kazumi Nishimura

Plasma outflows from gamma-ray bursts (GRB), pulsar winds, relativistic jets, and ultra-intense laser targets radiate high energy photons. However, radiation damping is ignored in conventional PIC simulations. In this letter, we study the radiation damping effect on particle acceleration via Poynting fluxes in two-and-half-dimensional particle-in-cell (PIC) plasma simulation of electron-positron plasmas. Read More

Affiliations: 1Rice University, Houston, TX, 2Los Alamos National Laboratory, Los Alamos, NM
Category: Astrophysics

The diverse and complex light curves of gamma-ray bursts (GRBs) remain an outstanding astrophysical mystery. Here we report the results of 2-1/2-dimensional particle-in-cell (PIC) simulations of the relativistic expansion of magnetized electron-positron plasmas. When the simulation is carried to >150 light-crossing time of the initial plasma, the plasma pulse reproduces many of the GRB features. Read More

Two-and-a-half-dimensional particle-in-cell plasma simulations are used to study the particle energization in expanding magnetized electron-positron plasmas with slab geometry. When the magnetized relativistic plasma with high temperature (initial electron and positron temperature are $k_{B}T_{e}=k_{B}T_{p}=5MeV$) is expanding into a vacuum, the electromagnetic (EM) pulse with large amplitude is formed and the surface plasma particles are efficiently accelerated in the forward direction owing to the energy conversion from the EM field to the plasma particles. We find that the behavior of the DRPA (Diamagnetic Relativistic Pulse Accelerator) depends strongly on the ratio of the electron plasma frequency to the cyclotron frequency $\omega_{pe}/\Omega_{e}$ and the initial plasma thickness. Read More

Charge separation effects in the expansion of magnetized relativistic electron-ion plasmas into a vacuum are examined using 2-1/2-dimensional particle-in-cell plasma simulations. The electrostatic field at the plasma surface decelerates electrons and accelerates ions. A fraction of the surface electrons are trapped and accelerated by the pondermotive force of the propagating electromagnetic pulse, a mechanism we call the DRPA (diamagnetic relativistic pulse accelerator). Read More

Using a 2-1/2-dimensional particle-in-cell (PIC) code to simulate the relativistic expansion of a magnetized collisionless plasma into a vacuum, we report a new mechanism in which the magnetic energy is efficiently converted into the directed kinetic energy of a small fraction of surface particles. We study this mechanism for both electron-positron and electron-ion (mi/me=100, me is the electron rest mass) plasmas. For the electron-positron case the pairs can be accelerated to ultra-relativistic energies. Read More