The role of pressure anisotropy in the turbulent intracluster medium

In low-density plasma environments, such as the intracluster medium (ICM), the Larmour frequency is much larger than the ion-ion collision frequency. In such a case, the thermal pressure becomes anisotropic with respect to the magnetic field orientation and the evolution of the turbulent gas is more correctly described by a kinetic approach. A possible description of these collisionless scenarios is given by the so-called kinetic magnetohydrodynamic (KMHD) formalism, in which particles freely stream along the field lines, while moving with the field lines in the perpendicular direction. In this way a fluid-like behavior in the perpendicular plane is restored. In this work, we study fast growing magnetic fluctuations in the smallest scales which operate in the collisionless plasma that fills the ICM. In particular, we focus on the impact of a particular evolution of the pressure anisotropy and its implications for the turbulent dynamics of observables under the conditions prevailing in the ICM. We present results from numerical simulations and compare the results which those obtained using an MHD formalism.Comment: 7 pages, 14 figures, Journal of Physics: Conference Serie

Features of collisionless turbulence in the intracluster medium from simulated Faraday Rotation maps

Observations of the intracluster medium (ICM) in galaxy clusters suggest for the presence of turbulence and the magnetic fields existence has been proved through observations of Faraday Rotation and synchrotron emission. The ICM is also known to be filled by a rarefied weakly collisional plasma. In this work we study the possible signatures left on Faraday Rotation maps by collisionless instabilities. For this purpose we use a numerical approach to investigate the dynamics of the turbulence in collisionless plasmas based on an magnetohydrodynamical (MHD) formalism taking into account different levels of pressure anisotropy. We consider models covering the sub/super-Alfv\'enic and trans/supersonic regimes, one of them representing the fiducial conditions corresponding to the ICM. From the simulated models we compute Faraday Rotation maps and analyze several statistical indicators in order to characterize the magnetic field structure and compare the results obtained with the collisionless model to those obtained using standard collisional MHD framework. We find that important imprints of the pressure anisotropy prevails in the magnetic field and also manifest in the associated Faraday Rotation maps which evidence smaller correlation lengths in the collisionless MHD case. These points are remarkably noticeable for the case mimicking the conditions prevailing in ICM. Nevertheless, in this study we have neglected the decrease of pressure anisotropy due to the feedback of the instabilities that naturally arise in collisionless plasmas at small scales. This decrease may not affect the statistical imprint differences described above, but should be examined elsewhere.Comment: 24 pages, 15 figures, MNRAS accepte

Deposition of tin film on carbon steel bandsaw blades by the cold plasma tecnique.

Disponível online. Resumo

Extração de RNA total de folhas de algodoeiro.

bitstream/CNPA/20893/1/CIRTEC113.pd

Qualidades de maçã Maxigala influenciadas pela irrigação e fertirrigação.

O objetivo deste trabalho foi avaliar o efeito da irrigação e fertirrigação na qualidade de frutos de macieiras

Desenvolvimento do Webservice EGENT - Estudo Gráfico da Evolução dos N-Grams no Tempo.

Este trabalho apresenta um conjunto de ferramentas computacionais para o mapeamento da cobertura temporal de n-grams e termos de um domínio específico do conhecimento agrícola. A partir de um corpus textual formado por textos enriquecidos com metadados anotados automaticamente sobre a cultura de cana-de-açúcar tais ferramentas criam e apresentam a evolução do uso dos termos ao longo tempo. Além dos metadados, e usando o programa REMBRANDT também foram mapeadas a Entidades Mencionadas com classe de Tempo constantes nos conteúdos de texto para futuras análises semânticas a partir destas marcações. Os resultados são bastante satisfatórios e podem ser analisados sob o aspecto estratégico, cuja análise pode ser feita do ponto de vista do alcance dos objetivos propostos e seus trabalhos futuros, e outro mais prático cuja análise foca o ambiente operacional das ferramentas produzidas.CIIC 2012. No 12616

MHD turbulence-Star Formation Connection: from pc to kpc scales

The transport of magnetic flux to outside of collapsing molecular clouds is a required step to allow the formation of stars. Although ambipolar diffusion is often regarded as a key mechanism for that, it has been recently argued that it may not be efficient enough. In this review, we discuss the role that MHD turbulence plays in the transport of magnetic flux in star forming flows. In particular, based on recent advances in the theory of fast magnetic reconnection in turbulent flows, we will show results of three-dimensional numerical simulations that indicate that the diffusion of magnetic field induced by turbulent reconnection can be a very efficient mechanism, especially in the early stages of cloud collapse and star formation. To conclude, we will also briefly discuss the turbulence-star formation connection and feedback in different astrophysical environments: from galactic to cluster of galaxy scales.Comment: 6 pages, 5 figures, 274 IAU Symposium: Advances in Plasma Astrophysic