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The role of turbulence in astrophysical environments and its interplay with magnetic fields is still highly debated. In this lecture, we will discuss this issue in the framework of dynamo processes. We will first present a very brief summary of turbulent dynamo theories, then will focus on small scale turbulent dynamos and their particular relevance on the origin and maintenance of magnetic fields in the intra-cluster media (ICM) of galaxies. In these environments, the very low density of the flow requires a collisionless-MHD treatment. We will show the implications of this approach in the turbulent amplification of the magnetic fields in these environments. To finalize, we will also briefly address the connection between MHD turbulence and fast magnetic reconnection and its possible implications in the diffusion of magnetic flux in the dynamo process. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

When the winds of two massive stars orbiting each other collide, an interaction zone is created consisting of two shock fronts at both sides of a contact surface. During the cooling process, elements may recombine generating spectral lines. These lines may be Doppler shifted, as the gas stream flows over the interaction zone. To calculate the stream velocity projected into the line of sight we use a simplified conical geometry for the shock fronts and, to determine the synthetic line profile, we have to sum the amount of emitting gas elements with the same Doppler shifted velocity. We show that the stellar mass loss rates and wind velocities, and the orbital inclination and eccentricity, are the main parameters on this physical process. By comparing observational data to the synthetic line profiles it is possible to determine these parameters. We tested this process to Brey 22 WR binary system, and applied to the enigmatic object of η Carinae. [ABSTRACT FROM PUBLISHER]

The standard magnetohydrodynamic (MHD) description of the plasma in the hot, magnetized gas of the intra-cluster (ICM) medium is not adequate because it is weakly collisional. In such collisionless magnetized gas, the microscopic velocity distribution of the particles is not isotropic, giving rise to kinetic effects on the dynamical scales. These kinetic effects could be important in understanding the turbulence as well as the amplification and maintenance of the magnetic fields in the ICM. It is possible to formulate fluid models for collisonless or weakly collisional gas by introducing modifications in the MHD equations. These models are often referred as kinetic MHD (KMHD). Using a KMHD model based on the CGL-closure, which allows the adiabatic evolution of the two components of the pressure tensor (the parallel and perpendicular components with respect to the local magnetic field), we performed 3D numerical simulations of forced turbulence in order to study the amplification of an initially weak seed magnetic field. We found that the growth rate of the magnetic energy is comparable to that of the ordinary MHD turbulent dynamo, but the magnetic energy saturates in a level smaller than that of the MHD case. We also found that a necessary condition for the dynamo to operate is to impose constraints on the anisotropy of the pressure. [ABSTRACT FROM PUBLISHER]

In this work we propose the Bardeen-Petterson effect as the precession mechanism of the jet precession in NGC 1275. To check if this is true we have estimated the angular momentum ratio and the aligment timescale predict by the theory and compared with the numerical results presented in the literature. We were able to explain the precession period assuming an accretion disk with column surface density in the form of a power law with exponent 0.6 < s < 0.7 and a black hole rotation with a spin of 0.23 < a∗<0.4. [ABSTRACT FROM PUBLISHER]

It is well known that the interstellar (ISM) and intergalactic (ICM) media are threaded by large scale magnetic fields. The understanding of its role on the dynamics of the media is, however, still in progress. For the ISM, magnetic fields may control or, at least, play a major role on the turbulence cascade leading to the star formation process. The ICM, on the other hand, is assumed to be thermally dominated but still the magnetic field may play an important role on the processes of acceleration and propagation of cosmic rays. In this work we provide a review of the latest theoretical results on the evolution of MHD turbulence under collisional and collisionless plasma approaches. [ABSTRACT FROM PUBLISHER]

Star forming galaxies often exhibit hot halos with structures that resemble chimneys and fountains extending for several kpc above the galaxy. Observations indicate that they are probably produced by supernovae (SNe) which blow superbubbles that carve holes in the disk. Through these holes, high speed material is injected and expands buoyantly up to a maximum height and then returns to the disk pulled by the galaxy gravity. This circulating gas in a fountain tends to condense out forming high-velocity clouds and filaments. Starburst galaxies also show evidence that the spectacular winds that arise from their disk are fed by SNe explosions. Similarly, at galaxy cluster scales, most massive clusters exhibit rich filamentary structure of ionized gas which is distributed all around the central galaxy. We discuss here the role that SNe bubbles play in driving outflows and filamentary structures both at galaxy and galaxy-cluster scales. With the help of HD and MHD numerical simulations, we show in particular that SN-driven turbulence may play a key role at helping a central AGN halting and ”isotropize” the cooling flow in the central regions of a galaxy cluster. [ABSTRACT FROM PUBLISHER]

In this work, we present 3D MHD simulations of non-helical, forced turbulence, with an anisotropic thermal pressure with respect to the orientation of the local magnetic field. Such anisotropy arises when the plasma is weakly collisional, i.e., when the Larmor frequency is much greater than the ion-ion collision frequency. In this Kinetic MHD regime (KMHD), there are instabilities that give rise to fast growing magnetic fluctuations in the smallest scales. The plasma that fills the intergalactic and intracluster media has small density (n ~ 10−3cm−3), hence the effects of these instabilities could be important in the turbulent amplification of the magnetic fields there. In order to study the KMHD turbulence, we have performed 3D numerical simulations employing a godunov-MHD code (e.g., Kowal, Lazarian & Beresnyak 2007; Falceta-Gonçalves, Lazarian & Kowal 2008). The power spectrum of the velocity and magnetic fields were calculated for two cases: when there is a pre-existing mean magnetic field, and when there is only an initial weak magnetic field. [ABSTRACT FROM PUBLISHER]

Considering that the main source of turbulence in the ISM medium are the explosions of supernovae (SNe), we explore here the role of SN shock front interactions with clouds on the star formation triggering in presence and in absence of magnetic field. [ABSTRACT FROM PUBLISHER]