Eigenmodes and growth rates of relativistic current filamentation instability in a collisional plasma

I theoretically found eigenmodes and growth rates of relativistic current filamentation instability in collisional regimes, deriving a generalized dispersion relation from self-consistent beam-Maxwell equations. For symmetrically counterstreaming, fully relativistic electron currents, the collisional coupling between electrons and ions creates the unstable modes of growing oscillation and wave, which stand out for long-wavelength perturbations. In the stronger collisional regime, the growing oscillatory mode tends to be dominant for all wavelengths. In the collisionless limit, those modes vanish, while maintaining another purely growing mode that exactly coincides with a standard relativistic Weibel mode. It is also shown that the effects of electron-electron collisions and thermal spread lower the growth rate of the relativistic Weibel instability. The present mechanisms of filamentation dynamics are essential for transport of homogeneous electron beam produced by the interaction of high power laser pulses with plasma.Comment: 44 pages, 12 figures. Accepted for publication in Phys. Rev.

Improved intra-species collision models for PIC simulations

In recent years, the authors have investigated methods to improve the effectiveness of modeling collisional processes in particle-in-cell codes. Through the use of generalized collision models, plasma dynamics can be followed both in the regime of nearly collisionless plasmas as well as in the hydrodynamic limit of collisional plasmas. They have developed a collision-field method to treat both the case of collisions between unlike plasma species (inter-species collisions), through the use of a deterministic, grid-based force, and between particles of the same species (intra-species collisions), through the use of a Langevin equation. While the approach used for inter-species collisions is noise-free in that the collision experienced by a particle does not require any random numbers, such random numbers are used for intra-species collisions. This gives rise to a stochastic cooling effect inherent in the Langevin approach. In this paper, the authors concentrate on intra-species collisions and describe how the accuracy of the model can be improved by appropriate corrections to velocity and spatial moments

Recursos minerais não-metálicos

OS RECURSOS minerais não-metálicos, embora muito importantes para o atendimento das necessidades da população e para o comércio exterior, são pouco contemplados pelas ações governamentais e ignorados pelo público. Geralmente não-incluída no planejamento territorial, a mineração de não-metálicos no Brasil causa extensos impactos ambientais mal controlados. Propõe-se uma ação coordenada de fomento e controle patrimonial e ambiental da mineração, que só será conseguida por ação política, a qual depende da formação abrangente dos profissionais da mineração e de sua maior comunicação com a totalidade da população.<br>NONMETALLIC mineral resources, albeit very important for the needs of the population and for exportation, are ill-favored by governmental actions and ignored by the public. Generally not included in territorial planning, the mining of nonmetallic minerals in Brazil produces extensive, ill-controlled environmental impacts. A coordinated action of promotion and control, both patrimonial and environmental of mining, is proposed. This will only be achieved by political action, which depends on a more comprehensive education of mining professionals and on a greater communication by them with the population as a whole