Hideaki Takabe - Institute of Laser Engineering Osaka University

Hideaki Takabe
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Name
Hideaki Takabe
Affiliation
Institute of Laser Engineering Osaka University
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Astrophysics (7)
 
High Energy Astrophysical Phenomena (3)
 
High Energy Physics - Phenomenology (3)
 
Physics - Plasma Physics (2)
 
Solar and Stellar Astrophysics (1)
 
Physics - Space Physics (1)
 
Instrumentation and Methods for Astrophysics (1)

Publications Authored By Hideaki Takabe

In our contribution we give a brief overview of two widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.m.) (e. Read More

This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field or generalized Breit-Wheeler process, and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. Read More

Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Read More

A two-dimensional particle-in-cell simulation is performed to investigate weakly magnetized perpendicular shocks with a magnetization parameter of 6 x 10^-5, which is equivalent to a high Alfv\'en Mach number M_A of ~130. It is shown that current filaments form in the foot region of the shock due to the ion-beam--Weibel instability (or the ion filamentation instability) and that they generate a strong magnetic field there. In the downstream region, these current filaments also generate a tangled magnetic field that is typically 15 times stronger than the upstream magnetic field. Read More

A two-dimensional electromagnetic particle-in-cell simulation with the realistic ion-to-electron mass ratio of 1836 is carried out to investigate the electrostatic collisionless shocks in relatively high-speed (~3000 km s^-1) plasma flows and also the influence of both electrostatic and electromagnetic instabilities, which can develop around the shocks, on the shock dynamics. It is shown that the electrostatic ion-ion instability can develop in front of the shocks, where the plasma is under counter-streaming condition, with highly oblique wave vectors as was shown previously. The electrostatic potential generated by the electrostatic ion-ion instability propagating obliquely to the shock surface becomes comparable with the shock potential and finally the shock structure is destroyed. Read More

Laboratory spectroscopy of non-thermal equilibrium plasmas photoionized by intense radiation is a key to understanding compact objects, such as black holes, based on astronomical observations. This paper describes an experiment to study photoionizing plasmas in laboratory under well-defined and genuine conditions. Photoionized plasma is here generated using a 0. Read More

Supercritical accretion flows inevitably produce radiation-pressure driven outflows, which will Compton up-scatter soft photons from the underlying accretion flow, thereby making hard emission. We perform two dimensional radiation hydrodynamic simulations of supercritical accretion flows and outflows, incorporating such Compton scattering effects, and demonstrate that there appears a new hard spectral state at higher photon luminosities than that of the slim-disk state. In this state, as the photon luminosity increases, the photon index decreases and the fraction of the hard emission increases. Read More

We show that the Weibel-mediated collisionless shocks are driven at non-relativistic propagation speed (0.1c < V < 0.45c) in unmagnetized electron-ion plasmas by performing two-dimensional particle-in-cell simulations. Read More

We investigate numerically the hydrodynamic instability of an ionization front (IF) accelerating into a molecular cloud, with imposed initial perturbations of different amplitudes. When the initial amplitude is small, the imposed perturbation is completely stabilized and does not grow. When the initial perturbation amplitude is large enough, roughly the ratio of the initial amplitude to wavelength is greater than 0. Read More

We report the Compton scattering emission from the Poynting flux acceleration of electron- positron plasma simulated by the 2-1/2 dimensional particle-in-cell(PIC) code. We show these and other remarkable properties of Poynting flux acceleration and Compton spectral output, and discuss the agreement with the observed spectra of GRBs and XRFs. Read More

We investigate the stability of differentially rotating proto-neutron stars (PNSs) with a toroidal magnetic field. Stability criteria for nonaxisymmetric MHD instabilities are derived using a local linear analysis. PNSs are expected to have much stronger radial shear in the rotation velocity compared to normal stars. Read More

2004Nov
Affiliations: 1Institute of Laser Engineering Osaka University, 2University of California, Lawrence Livermore National Laboratory, 3Department of Astronomy, University of Maryland, 4University of California, Lawrence Livermore National Laboratory, 5University of California, Lawrence Livermore National Laboratory, 6Institute of Laser Engineering Osaka University
Category: Astrophysics

We investigate hydrodynamic instability of accelerating ionization fronts using two dimensional hydrodynamic simulations that include detailed energy deposition and release due to the absorption of UV radiation, recombination of hydrogen, radiative molecular cooling, and magnetic pressure. We consider linear perturbation growth and find that the stabilization mechanism associated with non-accelerated fronts remains a significant factor even when acceleration is present. Conversely, if recombination in the ionized region is turned off,Rayleigh-Taylor (RT) instability becomes effective, and the classical RT growth rate recovered. Read More

2004Feb
Affiliations: 1ILE, Osaka Univ., 2Waseda Univ., 3ILE, Osaka Univ.
Category: Astrophysics

We investigate the dynamics and morphology of jets propagating into the interstellar medium using 2D relativistic hydrodynamic simulations. The calculations are performed assuming axisymmetric geometry and trace a long propagation of jets. The jets are assumed to be 'light' with the density ratio between the beam to the ambient gas much less than unity. Read More

2001Oct
Affiliations: 1Institute of Laser Engineering, Osaka University, 2Institute of Laser Engineering, Osaka University, 3Institute of Laser Engineering, Osaka University
Category: Astrophysics

In this paper we present a numerical study of plasma jets produced by intense laser matter interactions. Through this study we hope to better understand astrophysical jets and their recent experimental simulations in the laboratory. We paid special attention to radiation cooling and the interaction of the jet with ambient gas. Read More