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.

Heating and acceleration of heavy ions in the solar wind and corona represent a long-standing theoretical problem in space physics and are distinct experimental signatures of kinetic processes occurring in collisionless plasmas. To address this problem, we propose the use of a low-noise hybrid-Vlasov code in four dimensional phase space (1D in physical space and 3D in velocity space) configuration. We trigger a turbulent cascade injecting the energy at large wavelengths and analyze the role of kinetic effects along the development of the energy spectra. Following the evolution of both proton and α distribution functions shows that both the ion species significantly depart from the maxwellian equilibrium, with the appearance of beams of accelerated particles in the direction parallel to the background magnetic field.

Jets can contribute to the spectra of X-ray binaries (XRBs) and active galactic nuclei (AGN) from the radio through the γ-ray bands; thus understanding their physics is key for interpreting the data. Recent VLBI observations suggest that jets begin to accelerate particles into power-law distributions at a point offset from the black hole by ~104rg, possibly via a collimation shock. Spectral fitting of simultaneous, broadband data from both XRBs and AGN in jet-dominated states corroborates this picture. From a magnetohydrodynamical (MHD) point of view, it is natural to associate the onset of particle acceleration with the final MHD critical point in the flow, the modified fast point (MFP), where causal contact with the upstream flow is broken. In this way a standing disruption like a shock can form, and this location might vary with the physical parameters of the jet. In order to study this issue, we have used the self-similar formalism of Vlahakis & Königl (2003, hereafter VK03) to simplify the MHD equations and to derive solutions that cross the critical points. We have found a new parameter space of solutions that cross the MFP at a finite height above the disc and are relativistic, spanning a range of Lorentz factors Γ ≤ 10 (Polko et al. 2010). We present these results, as well as preliminary work connecting the relativistic formalism to the non-relativistic conditions with gravity near the base of the jets.

Two-dimensional emission line images of the HH30 jet were recently used (De Colle et al. 2010) to recover the three-dimensional structure of the jet by applying standard tomographic technique (“Tikhonov regularization techniques”). In this paper I show that it is possible to determine the ejection history of the HH30 jet by directly comparing the outcome of numerical simulations with the results of the tomographic inversion. In particular, it is shown that the HH30 jet electron density map is best reproduced by assuming a velocity variation at the base of the jet with a large scale periodicity (with a period of ~3 yrs) added to small scales velocity variation (with periods ≲months).

We search for extended regions of radio emission not associated with Active Galactic Nuclei, known as ‘relics’, ‘halos’ and ‘mini halos’, in a sample of 70 Abell clusters for which we have radio, optical and X-ray data. AGN can produce particle bubbles of non-thermal emission, which can restrict cosmic rays. Hence, radio relics and (mini) halos could be forming as a result of the confinement of cosmic rays by these bubbles. We are probing the role that intracluster magnetic fields (using Faraday rotation measure and inverse compton arguments), mergers (through radio/X-ray interactions), cooling flows (X-ray data), radio jets/shocks, as well as radio (mini) halos/relics, play in the formation, acceleration, and propagation of cosmic rays. For the current study, we have selected two powerful nearby radio galaxies from our sample: Hercules A and 3C 388. We report on the work in progress and future plans.

It is shown that the magnetic current-driven (‘kink-type’) instability produces flow and field patterns with helicity and even with α-effect but only if the magnetic background field possesses non-vanishing current helicity B⋅ curl B by itself. Fields with positive large-scale current helicity lead to negative small-scale kinetic helicity. The resulting α-effect is positive. These results are very strict for cylindric setups without z-dependence of the background fields. The sign rules also hold for the more complicated cases in spheres where the toroidal fields are the result of the action of differential rotation (induced from fossil poloidal fields) at least for the case that the global rotation is switched off after the onset of the instability.

This paper provides an overview of the ESA Planck mission and its scientific promises. Planck is equipped with a 1.5–m effective aperture telescope with two actively-cooled instruments observing the sky in nine frequency channels from 30 GHz to 857 GHz: the Low Frequency Instrument (LFI) operating at 20 K with pseudo-correlation radiometers, and the High Frequency Instrument (HFI) with bolometers operating at 100 mK. After the successful launch in May 2009, Planck has already mapped the sky twice (at the time of writing this review) with the expected behavior and it is planned to complete at least two further all-sky surveys. The first scientific results, consisting of an Early Release Compact Source Catalog (ERCSC) and in about twenty papers on instrument performance in flight, data analysis pipeline, and main astrophysical results, will be released on January 2011. The first publications of the main cosmological implications are expected in 2012.

MHD Turbulence is a critical component of the current paradigms of star formation, particle transport, magnetic reconnection and evolution of the ISM, to name just a few. Progress on this difficult subject is made via numerical simulations and observational studies, however in order to connect these two, statistical methods are required. This calls for new statistical tools to be developed in order to study turbulence in the interstellar medium. Here we briefly review some of the recently developed statistics that focus on characterizing gas compressibility and magnetization and their uses to interstellar studies.

The quasar J1819+3845 has shown extreme variability with flux density variations in the radio regime up to 600% in less than one hour. In case of intrinsic high varibility, the short time scale sets a limit on the size of the emitting region and allows to estimate its brightness temperature. This would exceed 1021 K in the case of J1819+3845. Even an high relativistic jet beamed and doppler boosted in our line of sight cannot explain such an extreme violation of the Inverse Compton limit (1012 K). The variability of this source has been proven to be due to scattering in the Interstellar medium by a number of different experiments. Such an explanation requires a closeby scattering screen (few parsecs) and it results in a brightness temperature of about 1014 K. Many observing campaigns have been carried on to map the innermost jet structures of J1819+3845. Here we present the results of a number of VLBI observations, including space VLBI, to search for the missing jet in this puzzling source.

We present a model for high-energy flares in accreting black holes based on the injection in a magnetized corona of a non-thermal population of relativistic particles. Coupled transport equations are solved for all species of particles and the electromagnetic and neutrino output is predicted for the case of Galactic black holes.

The observed X-ray luminosity of SS 433 is ~1036 erg/s, it is known that all the radiation is formed in the famous SS 433 jets. The bolometric luminosity of SS 433 is ~1040 erg/s, and originally the luminosity must be realized in X-rays. The original radiation is probably thermalized in the supercritical accretion disk wind, however the missing more than four orders of magnitude is surprising. We have analysed the XMM-Newton spectra of SS 433 using a model of adiabatically and radiatively cooling X-ray jets. The multi-temperature thermal jet model reproduces very well the strongest observed emission lines, but it can not reproduce the continuum radiation and some spectral features. We have found a notable contribution of ionized reflection to the spectrum in the energy range from ~3 to 12 keV. The reflected spectrum is an evidence of the supercritical disk funnel, where the illuminating radiation comes from deeper funnel regions, to be further reflected in the outer visible funnel walls (r ≥ 2 ⋅ 1011 cm). The illuminating spectrum is similar to that observed in ULXs, its luminosity has to be no less than ~1039 erg/s. A soft excess has been detected, that does not depend on the thermal jet model details. It may be represented as a BB with a temperature of Tbb ≈ 0.1 keV and luminosity of Lbb~3 ⋅ 1037 erg/s. The soft spectral component has about the same parameters as those found in ULXs.

Numerical aspects of dynamos in periodic domains are discussed. Modifications of the solutions by numerically motivated alterations of the equations are being reviewed using the examples of magnetic hyperdiffusion and artificial diffusion when advancing the magnetic field in its Euler potential representation. The importance of using integral kernel formulations in mean-field dynamo theory is emphasized in cases where the dynamo growth rate becomes comparable with the inverse turnover time. Finally, the significance of microscopic magnetic Prandtl number in controlling the conversion from kinetic to magnetic energy is highlighted.

Microquasars are X-ray binaries that show extended radio jets. These jets can accelerate particles up to relativistic energies that produce non-thermal emission from radio to TeV, and could also make a non-negligible contribution to the galactic CRs in some energy ranges. The orbital motion and compactness of these sources allow the study of high-energy astrophysical phenomena in extreme conditions that change in accessible timescales. In this work, I briefly discuss the production of broadband non-thermal emission in microquasars, putting special emphasis on the high- and the very high-energy bands.

We are developing a spherical hybrid model to study how the solar wind interacts with the solar system bodies. In this brief status report we introduce some lessons from the spherical grid development and illustrate the usage of the new model by showing a preliminary test run.

The importance of reconnection in astrophysics has been widely recognized. It is instrumental in storing and releasing magnetic energy, the latter often in a dramatic fashion. A closely related process, playing in very low beta plasmas, is much less known. It is behind the acceleration of auroral particles in the low-density environment several 1000 km above the Earth. It involves the appearance of field-parallel voltages in presence of intense field-aligned currents. The underlying physical process is the release of magnetic shear stresses and conversion of the liberated magnetic energy into kinetic energy of the particles creating auroral arcs. In this process, field lines disconnect from the field anchored in the ionosphere and reconnect to other field lines. Because of the stiffness of the magnetic field, the process resembles mechanical fractures. It is typically active in the low-density magnetosphere of planets. However, it can also lead to significant energy conversion with high-energy particle production and subsequent gamma ray emissions in stellar magnetic fields, in particular of compact objects.

The impact of the Fermi Gamma-ray Space Telescope on blazar research is reviewed. This includes a brief description of the Fermi Large Area Telescope, a summary of the various classes of extragalactic sources found in the First Large Area Telescope AGN Catalog, and more detailed discussion of the flat spectrum radio quasar 3C454.3 and the BL Lac object PKS 2155-304. Some theoretical studies related to ongoing blazar research with Fermi are mentioned, including implications of γ-ray observations of radio galaxies on blazar unification scenarios, variability in colliding shells, and whether blazars are sources of ultra-high energy cosmic rays.

The ALMA (Atacama Large Millimeter/sub-millimeter Array) is the large interferometer that will consist up to 64 high-precision antennas operating in the 31.3 – 950 GHz frequency range. In this range unique observations in cosmology, cold universe, galaxies, stars and their formations, and so on are expected. Among these objectives there is a unique possibility to observe the Sun and to address outstanding issues of solar physics. The ALMA is shortly described and then the new ESO-ALMA European node (ARC) built at Ondřejov Observatory is presented. The new ARC is the only one in Europe oriented to solar physics. The requirements and limitations for ALMA solar observations, as well as some examples of possible solar-oriented ALMA projects, are mentioned.

One of the challenges in constructing global magnetohydrodynamic (MHD) models of the inner heliosphere for, e.g., space weather forecasting purposes, is to correctly capture the acceleration and expansion of the solar wind. In many current models, the solar wind is driven by varying the polytropic index so that a desired heating is obtained. While such schemes can yield solar wind properties consistent with observations, they are not problem-free. In this work, we demonstrate by performing MHD simulations that altering the polytropic index affects the properties of propagating shocks significantly, which in turn affect the predicted space weather conditions. Thus, driving the solar wind with such a mechanism should be used with care in simulations where correctly capturing the shock physics is essential. As a remedy, we present a simple heating function formulation by which the polytropic wind can be used while still modeling the shock physics correctly.

Observations of plasma and magnetic field fluctuations in the solar wind provide a valuable source of information for the study of turbulence in collisionless astrophysical plasmas. Scientific data collected by various spacecraft over the last few decades has fueled steady progress in this field. Theoretical models, numerical simulations, and comparisons between theory and experiment have also contributed greatly to these advances. This review highlights some recent advances on the observational side including measurements of the anisotropy of inertial range fluctuations as revealed by the different scaling laws parallel and perpendicular to the mean magnetic field, measurements of the normalized cross-helicity spanning the entire inertial range which demonstrate that this quantity is scale invariant, and improved measurements of the spectrum of magnetic field fluctuations in the dissipation range that show a spectral break near the lengthscale of the electron gyro-radius. The theoretical implications of these results and comparisons between theory and observations are briefly summarized.

The jets image modelling of gravitationally lensed sources have been performed. Several basic models of the lens mass distribution were considered, in particular, a singular isothermal ellipsoid, an isothermal ellipsoid with the core, different multi-components models with the galactic disk, halo and bulge. The obtained jet images were compared as with each other as with results of observations. A significant dependence of the Hubble constant on the model parameters was revealed for B0218+357, when the circular structure was took into account.