Three-Dimensional Particle Acceleration in Electromagnetic Cylinder and Torus

Particle acceleration via Poynting vector with toroidal magnetic field is studied in 3D PIC simulation of electron-positron plasma. We choose two different initial magnetic field configurations to compare how the particle acceleration is affected by the expansion of electromagnetic wave. In the cylindrical case, the electromagnetic field strength decays as (ct)⁻², and particles are accelerated in the radial direction as well as the axial direction. Rayleigh-Taylor instability is also observed at the center of the cylinder. In the torus case, the field strength decays as (ct)⁻³, making the acceleration less efficient. Particles accelerated in the axial direction by E × B force creates strong charge separation.     

Monte Carlo simulation of pair creation using petawatt lasers

Irradiating high-Z targets such as gold with ultra-intense lasers creates electron-positron pairs. In particular, the positron density in the plasma created by this procedure is higher than that obtained via other laboratory-based methods, with theoretical maximum densities exceeding 10¹⁸ cm⁻³. All of the significantly contributing processes are well-known and hence we can study this phenomenon using Monte Carlo simulation. We focus on the latter part of this procedure, the passage of high-energy electrons through the target creating pairs. In particular, we discuss the usefulness of CERN’s GEANT4 Monte Carlo code in simulating this process. Once this code is successfully calibrated, we will use it to perform parameter studies, and design future targets to optimize the positron yield.     

Applications of laser-created dense e<Superscript>+</Superscript>e<Superscript>−</Superscript> pairs

We review the recent developments of laser pair creation in the laboratory and their potential applications to astrophysics and other frontiers. Many astrophysical phenomena involving e⁺e⁻ plasmas may be systematically investigated in the laboratory setting. We also discuss potential applications of dense positronium gas.     

Models of soft gamma-ray repeater emissions

We review emission models of soft gamma-ray repeaters (SGRs) within the context of magnetized neutron star origins. Motivations for moderate field (10^10–12G) versus ultrastrong field ( 5 × 10¹⁴G) neutron stars are considered. Implications for the astrophyiscal models are discussed.     

Extraction of tsunami source coefficients via inversion of DART \circledR^{\circledR} buoy data

The ability to accurately forecast potential hazards posed to coastal communities by tsunamis generated seismically in both the near and far field requires knowledge of so-called source coefficients, from which the strength of a tsunami can be deduced. Seismic information alone can be used to set the source coefficients, but the values so derived reflect the dynamics of movement at or below the seabed and hence might not accurately describe how this motion is manifested in the overlaying water column. We describe here a method for refining source coefficient estimates based on seismic information by making use of data from Deep-ocean Assessment and Reporting of Tsunamis (DART ^\circledR^{\circledR}) buoys (tsunameters). The method involves using these data to adjust precomputed models via an inversion algorithm so that residuals between the adjusted models and the DART ^\circledR^{\circledR} data are as small as possible in a least squares sense. The inversion algorithm is statistically based and hence has the ability to assess uncertainty in the estimated source coefficients. We describe this inversion algorithm in detail and apply it to the November 2006 Kuril Islands event as a case study.     

A methodology for structural analysis and optimization of riser connection joints

In riser structural systems, the region where the riser is connected to the platform is critical due to the development of high stress levels. To reduce the stress concentration in this region, bend stiffeners and stress joints are used in order to provide a gradual stiffness transition between the riser and the platform. The present paper presents an optimization design approach for bend stiffeners and stress joints, using a slender beam procedure for the connection joint analysis and an evolution strategies multi-objective optimization algorithm. This approach produces similar results when compared to a finite element analysis of the complete riser, but with significant reduction of computational costs. Numerical examples are presented, showing the efficiency and robustness of the suggested methodology.     

Three-Dimensional Particle Acceleration in Electromagnetic Dominated Outflows with Background Plasma and Clump

The effect of background plasma on particle acceleration via Poynting fluxes is studied in 3D PIC simulation of electron-positron and electron-ion plasmas. When a strongly magnetized ejecta at the center expands to low-temperature electron-positron ambient plasma background and a low-density clump, electromagnetic wave front accelerates particles in the background and clump, and captures them in the Ponderomotive potential well. We do not observe any instability, and the momentum distributions of background and clump form a power law of slope close to −1.5 with a sharp peak in the middle. When an ejecta expands to the ion-electron interstellar medium (ISM), the acceleration via Poynting flux is severely damped due to the charge separation.     

Wealth and poverty in rural India

The main objectives of this paper are to identify and account for the regional variations in the rural household incomes and inequalities in income distribution between and within regions in India. Clearly, higher average incomes are concentrated in the W and NW regions, and very low incomes in the densely populated E and S. These differences have been analysed through the use of correlation and regression model, based on 15 variables. The results indicate that agricultural development (reflected in mechanization and irrigation), size of holdings, and family size have a positive influence on incomes, and landlessness negative. Further, a significant negative correlation between low caste population density and household incomes suggests that, at least, some of the impoverishment in the villages may be attributed to an unfair social structure that has developed and has been maintained over a long time in India. This conclusion is further reinforced by comparing income data from regions dominated by tribal social system and community ownership of land with those where Hindu caste system and private ownership of land are dominant.     

Particle Acceleration in Relativistic Magnetized Plasmas

We review the particle-in-cell simulation results related to the recently discovered particle acceleration mechanism called the Diamagnetic Relativistic Pulse Accelerator, or DRPA. This mechanism may be relevant to the prompt gamma-ray emission of gamma-ray bursts. It may also be testable with future laboratory experiments using ultra-intense lasers.