Planetary nebulae (PNe) often show large departures from spherical symmetry. The origin and development of these asymmetries is not clearly understood. The most striking structures are the highly collimated jets that are already observed in a number of evolved stars before they enter the PN phase. The aim of this project is to observe the Zeeman splitting of the OH maser of the W43A star and determine the magnetic field strength in the low density region. The 1612 MHz OH masers of W43A were observed with MERLIN to measure the circular polarization due to the Zeeman splitting of 1612 OH masers in the envelope of the evolved star W43A. We measured the circular polarization of the strongest 1612 OH masers of W43A and found a magnetic field strength of ~100μG. The magnetic field measured at the location of W43A OH masers confirms that a large scale magnetic field is present in W43A, which likely plays a role in collimating the jet.

The problem of the global stability of rotating magnetized thin disks is considered. The appropriate boundary value problem (BVP) of the linearized MHD equations is solved by employing the WKB approximation to describe the dynamical development of an initial perturbation. The eigenfrequencies as well as eigenfunctions are explicitly obtained and are verified numerically. The importance of considering the initial value problem (IVP) as well as the question of global stability for finite systems is emphasized and discussed in detail. It is further shown that thin enough disks are stable (global stability) but as their thickness grows increasing number of unstable modes participate in the solution of the IVP. However it is demonstrated that due to the localization of the initial perturbation the growth time of the instability may be significantly longer than the calculated inverse growth rate of the individual unstable eigenfunctions.

In this short note, we raise the issue how magnetic braking of prestellar and protostellar condensations depends on the metallicity of the molecular gas cloud. We suggest that the degree of ionization, which determines the timescale for redistribution of magnetic flux (ambipolar diffusion) in the dense cloud core, depends linearly on the heavy element and dust abundance of the gas. This implies that magnetic braking is less efficient in metal-poor condensations, and hence more of the angular momentum problem of star formation must be solved by other means, such as fragmentation into (wider) binary systems. Observations of orbital periods (separations) of binary systems among the metal-poor Galactic halo stars could test this prediction.

We find that the star formation is accelerated by the supersonic turbulence in the magnetically dominated (subcritical) clouds. We employ a fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally driven fragmentation of molecular clouds. The time-scale of collapsing core formation in subcritical clouds is a few ×107 years when starting with small subsonic perturbations. However, it is shortened to approximately several ×106 years by the supersonic flows in the clouds. We confirm that higher-spacial resolution simulations also show the same result.

We present 3D global MHD simulations of proto-planetary disks calculated with the ZeusMP code. We focus on gas dynamics; the magnetic diffusivity and temperature are fixed during the simulation. A zone with low gas ionization at the midplane is included within ±2 scale heights. We mimic the ‘snow’-line radius with one order of magnitude jump in magnetic diffusivity η. Resulting turbulent Maxwell and Reynolds stresses are present at the midplane despite of low ionization. We find no radial inhomogeneities in turbulent α stress for a mild ionization contrast at the ‘snow’-line. A smooth azimuthal magnetic field is produced in the dead zone which may be a driving force for a weak accretion flow.

In ultra dense and hot region realized in stellar core-collapse, neutrino takes major role in energy and momentum transports. We investigate the growth of magnetorotational instability (MRI) in neutrino viscous matter by using linear theory. It is found from the local linear analysis that the neutrino viscosity can suppress the MRI in the regime of weak magnetic field (B ≪ 1014G). This suggest that MHD turbulence sustained by the MRI might not be driven efficiently in the neutrino viscous media. Applying this result to collapsar disk, which is known as the central engine of gamma-ray burst (GRB), we find that the MRI can be suppressed only in its inner region. Based on this finding, a new evolutionary scenario of collapsar disk, “Episodic Disk Accretion Model” are proposed.

Axisymmetric MRI in viscous accretion disks is investigated. The linear growth of the viscous MRI is characterized by the Reynolds number RMRI ≡ v2A/νΩ, where vA is the Alfvén velocity, ν is the kinematic viscosity, and Ω is the angular velocity of the disk. Although the linear growth of the MRI is suppressed as the Reynolds number decreases, its nonlinear behavior is found to be almost independent of RMRI. At the nonlinear stage, the channel flow grows and the Maxwell stress increases even though RMRI is much smaller than unity. Nonlinear behavior of the MRI in the viscous regime can be explained by the characteristics of the linear dispersion relation. Applying our results to the case with both viscosity and resistivity, it is anticipated that the critical value of the Lundquist number SMRI ≡ v2A/ηΩ for active turbulence would depend on the magnetic Prandtl number Pm ≡ ν/η, where η is the magnetic diffusivity.

We construct a magnetic reconnection model for magnetar giant flare in the framework of solar flare/coronal mass ejection theory. As is the case with the solar flare, the explosive magnetic reconnection plays a crucial role in the energetics of the magnetar flare. A key physics controlling the energy transport in the system, on the other hand, is the radiative process unlike that in the solar flare. After the release of the magnetic energy via the magnetic reconnection, the radiative heat flux drives the baryonic evaporation. Our model can predict that the baryonic matter evaporated in the preflare stage would be the origin of the radio emitting ejecta observed in association with the giant flare on 2004 December 27 from SGR1806-20.

We present results of investigation of the off-equatorial circular orbits existence in the vicinity of neutron stars, Schwarzschild black holes with plasma ring, and near Kerr-Newman black holes and naked singularities.

A test field solution is constructed, describing the electromagnetic field around a Kerr black hole which is drifting in an arbitrary direction. An asymptotically uniform magnetic field is assumed with a general orientation (with respect to the rotation axis). Lines of force of electric and magnetic intensities are explored, as measured by an observer orbiting around the black hole (above the innermost stable circular orbit, ISCO) or freely falling (below the ISCO) down to the horizon. Magnetic null point is found.

It is widely accepted that quasars and other active galactic nuclei (AGN) are powered by accretion of matter onto a central supermassive black hole. While numerical simulations have demonstrated the importance of magnetic fields in generating the turbulence believed necessary for accretion, so far they have not produced the high mass accretion rates required to explain the most powerful sources. We describe new global 3D simulations we are developing to assess the importance of radiation and non-ideal MHD in generating magnetized outflows that can enhance the overall rates of angular momentum transport and mass accretion.

Observations of hot-spot thermal X-ray emission from radio pulsars implicate that surface magnetic field (SMF) at the polar cap is much stronger than the conventional dipolar component estimated from the pulsar spin-down. This strongly suggests that SMF is dominated by the crust anchored small scale magnetic field. We present the observed values of black body temperature and bolometric luminosity of X-ray emission from hot polar caps of a number of pulsars. In all cases the inferred value of SMF is close to 1014 G.

We present observational evidence that NGC 6543 produced a jet of cosmic rays that irradiated the Earth recorded as cosmogenic10Be found ice cores. This identification shows that the jet was accompanied by a magnetic field of sufficient strength to travel 220pc and retain evidence of the celestial coordinates of the source object.

We study the effects of hypercritical accretion onto a neutron star surface. The magnetic field submergence in the neutron star crust and the possible rediffusion is investigated.

VLT FORS 1 observations indicate the presence of a variable significant magnetic field in the X-ray binary Cyg X-1. The importance of this investigation comes from the fact that it rules one of the most significant BH manifestations: the X-ray millisecond flickering, usually related to reconnection of magnetic lines in the innermost part of the accretion disc.

Using special relativistic magnetohydrodynamic simulation, the nonlinear dynamics of the magnetized outflow triggered on the magnetar surface is investigated. It is found that the strong shock propagates in the circumstellar medium in association with the expanding outflow. The shock velocity vsh depends on the strength of the dipole field anchored to the stellar surface Bdipole and is described by a simple scaling relation vsh ∝ Bdipole0.5. In addition, the outflow-driven shock can be accelerated self-similarly to the relativistic velocity when the density profile of the circumstellar medium is steeper than the critical density profile, that is α ≡ d logρ(r)/d log r ≲ αcrit = −5.0, where the density is set as a power law distribution with an index α and r is the cylindrical radius. Our results suggest that the relativistic outflow would be driven by the flaring activity in a circumstellar medium with a steep density profile.

Radio continuum emission from the supernova remnant G296.5 + 10.0 was observed using the Australia Telescope Compact Array. Using a 104 MHz bandwidth split into 13 × 8 MHz spectral channels, it was possible to produce a pixel-by-pixel image of Rotation Measure (RM) across the entire remnant. A lack of correlation between RM and X-ray surface brightness reveals that the RMs originate from outside the remnant. Using this information, we will characterise the smooth component of the magnetic field within the supernova remnant and attempt to probe the magneto-ionic structure and turbulent scale sizes in the ISM and galactic halo along the line-of-sight.

Advances in helioseismology provide new knowledge about the origin of solar magnetic activity. The key questions addressed by helioseismology are: what is the physical mechanism of the solar dynamo, how deep inside the Sun are the magnetic fields generated, how are they transported to the surface and form sunspots? Direct helioseismic signatures of the internal magnetic fields are weak and difficult to detect. Therefore, most of the information comes from observations of dynamical effects caused by the magnetic fields. I review results of recent helioseismic observations of the magnetohydrodynamics of the solar interior on various scales, including global dynamics associated with the dynamo processes, and formation of sunspots and active regions.

Selected topics in solar dynamo theory are being highlighted. The possible relevance of the near-surface shear layer is discussed. The role of turbulent downward pumping is mentioned in connection with earlier concerns that a dynamo-generated magnetic field would be rapidly lost from the convection zone by magnetic buoyancy. It is argued that shear-mediated small-scale magnetic helicity fluxes are responsible for the success of some of the recent large-scale dynamo simulations. These fluxes help in disposing of excess small-scale magnetic helicity. This small-scale magnetic helicity, in turn, is generated in response to the production of an overall tilt in each Parker loop. Some preliminary calculations of this helicity flux are presented for a system with uniform shear. In the Sun the effects of magnetic helicity fluxes may be seen in coronal mass ejections shedding large amounts of magnetic helicity.

The solar tachocline is shown as hydrodynamically stable against nonaxisymmetric disturbances if it is true that no cos4θ term exists in its rotation law. We also show that the toroidal field of 200 Gauss amplitude which produces the tachocline in the magnetic theory of Rüdiger & Kitchatinov (1997) is stable against nonaxisymmetric MHD disturbances – but it becomes unstable for rotation periods slightly slower than 25 days. The instability of such weak fields lives from the high thermal diffusivity of stellar radiation zones compared with the magnetic diffusivity. The growth times, however, result as very long (of order of 105 rotation times). With estimations of the chemical mixing we find the maximal possible field amplitude to be ~500 Gauss in order to explain the observed lithium abundance of the Sun. Dynamos with such low field amplitudes should not be relevant for the solar activity cycle.

With nonlinear simulations of MHD Taylor-Couette flows it is shown that for the rotation-dominated magnetic instability the resulting eddy viscosity is only of the order of the molecular viscosity. The Schmidt number as the ratio of viscosity and chemical diffusion grows to values of ~20. For the majority of the stellar physics applications, the magnetic-dominated Tayler instability will be quenched by the stellar rotation.