List of abstracts

1 - Separable solutions of force-free spheres and applications to solar active regions.

A. Prasad

In this paper we present a systematic study of the force-free field equation for simple axisymmetric configurations in spherical geometry and apply it to study solar active regions. The condition of separability of solutions of the force-free field equation in radial and angular variables leads to two classes of solutions: linear and non-linear force-free fields. We have studied these linear solutions Chandrasekhar (1956) and extended the non-linear solutions given in Low & Lou (1990) to the irreducible rational form $n= p/q$, which is allowed for all cases of odd $p$ and to cases of $q>p$ for even $p$. We have further calculated the energies and relative helicities for these magnetic field configurations in finite and infinite shell geometries. We apply these solutions to simulate photospheric vector magnetograms which were obtained using the spectro-polarimeter onboard Hinode. Using the best fit models to these magnetograms, we build the full 3D field configurations for the solar corona and calculate the energy and relative helicity for active regions - NOAA AR 10923, 10930 and 10933. For the active region NOAA AR 10930 we analyzed 5 magnetograms spanning a period of 3 days during which two X class flares occurred. This enabled us to study the evolution of the free energy and relative helicity during the flare event. Our analysis indicates a peak in free energy and relative helicity before the flare events which decreases subsequently after the flare, consistent with our expectations. The trends thus predicted for the ARs are largely consistent with results mentioned in literature. This method thus provides a very useful tool to reconstruct non-linear force-free fields from the spectropolarimetric data of an AR and obtain quick estimates of their free energy and relative helicity. These solution can also serve as reasonably good exact input fields for testing other numerical techniques.

2 - Helicity Constrained Model of a Galactic Dynamo

A. Prasad

Magnetic fields correlated on kiloparsec scales are seen in disc galaxies. The origin could be due to amplification of small scale seed fields by a turbulent dynamo. Helicity conservation imposes constraints on dynamo action and one can study the minimal field strength of the large scale magnetic field that could arise despite the constraint. The calculation of helicity is technically complicated because of open boundaries and the usual form for the MHD invariant needs to be modified to take this into account. A general formalism has been developed to calculate the field strength using a quasi-linear dynamo model. As a first step, a galactic disk dynamo model has been built analytically while making the usual assumptions of shear and the \u03b1 effect. We find quadrupolar solutions that are matched to a vacuum/force-free field . The general approach to solving the quasi-linear dynamo using the full set of relative helicity boundary conditions are described.

3 - Evolution of Faraday rotation measure against X-ray flux of simulated galaxy clusters

Alvina Y. L. On

The large-scale magnetic fields permeating the Universe are weak and difficult to be observed. Little is known about the properties of magnetic fields in cosmological filaments and voids, superclusters and even galaxy clusters. At present, magnetic fields in the intra-cluster medium is diagnosed by correlating the Faraday rotation measures (RM) derived from the radio data and the X-ray flux (Fx) emitted from the cluster. Observations have shown that the standard deviation of RM (sigma(RM)) and Fx at each position in galaxy clusters tend to follow a power-law relationship. In this work, we quantify this relation and investigate its redshift dependence. We calculate the Fx and RM pixel-by-pixel in images of model galaxy clusters generated by the GCMHD+ simulations. By following the development and structural evolution of the clusters, we establish the redshift-dependent relation between Fx and sigma(RM). The coherence length of magnetic fields can be derived from the sigma(RM). Proper modelling of the time-dependent relation between Fx and RM for galaxy clusters is essential to probe the evolution of magnetic fields in cluster scales and beyond.

4 - High frequency waves in the solar atmosphere

Aneta Wisniewska

We investigate the propagation of high frequency waves in solar the atmosphere under magnetic and non magnetic environmental conditions. We carry out the observations with the newly developed instrument HELLRIDE at the Vacuum Tower Telescope, Tenerife (HELLRIDE: Helioseismologic Large Regions Interferometric Device). This instrument is currently unique in it's ability to measure quasi-simultaneously a large number of spectral lines over extended times.

5 - X-Ray Irradiated Accretion Disk

Bari Maqbool

We present here the mathematical approach in calculating the structural changes which take place in the outer regions of the accretion disk due to X-ray irradiation. It is shown here that an X-ray source powered by accretion, modifies the outer disc structure. Our calculations for the transition radius and Circularization Radius in case of various low mass X-ray binaries show that the X-ray irradiation becomes dominant after transition radius only in some binary systems.

6 - Using Rotation Measure Synthesis to Probe the Intrinsic Magnetoionic Environments of AGN

Craig Anderson

Using RM synthesis, it has been shown that up to 25% of polarised extragalactic radio sources show emission from multiple Faraday depths, or so-called 'complex' Faraday Depth Spectra (FDS). We are investigating whether it is possible to use complex FDS to 'super-resolve' intrinsic magnetoionic structures in spatially unresolved radio-loud AGN, via the spectropolarimetric imprint left by these structures on polarised emission. We present the results of an RM synthesis analysis of 600 compact radio sources observed from 1-3GHz. We discuss the sample in terms of the prevalence of complex FDS, the plausibility of modelling this behaviour as resulting from intrinsic magnetoionic source structure, and the correlation between Faraday complexity and multi-wavelength source properties.

7 - Magnetic fields in solar-type stars: new clues on the solar chemical composition from advanced 3D MHD atmospheric modelling

D. FABBIAN

What is the influence of the magnetic fields present in stars like our Sun on the elemental abundance derived from a comparison of observations and 3D MHD atmospheric models?

8 - Evolution of large-scale magnetic fields due to structure formation

David Barnes

Observations of galaxy clusters show $\mu\rm{G}$ strength magnetic fields permeating the intracluster medium and, despite the challenging nature of the observations, there is growing evidence of the presence of magnetic fields on the very large scale, such as in superclusters, cosmological filaments and voids. The origin of these magnetic fields is still unclear. Battery processes or phase transitions in the early universe may have seeded it with primordial cosmological magnetic fields. Alternatively, AGN and galactic outflows may pollute the universe with magnetic fields at later epochs. In order to gain a greater understanding of the resulting magnetized Universe produced by these different seed models, we require numerical magnetohydrodynamic (MHD) simulations. We use the smoothed particle MHD code GCMHD+ to perform simulations of large-scale structure formation seeded with a large-scale magnetic field. We investigate how mergers and the accretion of material on to a forming galaxy cluster causes mixing and amplification of the seed field. We compare the resulting magnetic field strength and topology of the simulated galaxy clusters to that of the observed clusters. We calculate the X-ray and radio fluxes of the simulated clusters and compare their ratio to the observed X-ray-radio relation.

9 - Launching Jets and Winds from turbulent alpha-omega-Dynamo Disks

Deniss Stepanovs

The role of magnetic fields in the context of accretion disks and the origin of jets cannot be underestimated. However, due to the complexity of the physical problem, its time evolution and geometrical structure is still under debate. It is the magnetic field which are crucial for generating winds and jets which then propagate far beyond their origin. We are running MHD simulations using PLUTO code to explore the launching, the formation, and the propagation of jets and winds out of the accretion disk. Previous simulations and semi-analytical calculations have shown that jets and winds could be produced by the interplay of large scale magnetic fields with a diffusive accretion disk. By applying a mean-field dynamo model to diffusive MHD accretion disks we are investigating the magnetic field structure which emerges from the dynamo process and which provides the launching mechanism for jets and outflows. We have found that in order to produce and sustain jets a localized region of relatively strong magnetic field is essential. We have showed that large scale phenomena like jets can easily emerge from a localised dynamo process. We have showed in detail how the localised dynamo produce a large scale magnetic field sufficiently strong to launch jets.

10 - Effects of a Meridional Flow Counter-Cell on the Solar Activity Cycle

E. C. Amouzou

The effects of varying the latitudinal extent and peak flow speed of a simulated polar counter-cell are determined by studying the resulting duration and intensity of the activity cycle.

11 - Long term variability of low mass X-ray binaries with late type giant companions

Filippova Ekaterina

In this work we propose a physical mechanism for generation of noise in mass accretion rate in low mass X-ray binaries (LMXB) with giant stars at large time scales. With 3D simulations we show that accretion from the stellar wind in such systems can result in variability of mass accretion rate with characteristic time scale close to the orbital period even with zero eccentricity of the binary. Our estimates show that observational appearance of the stellar wind is quite similar to one of accretion disk corona. This mechanism can be used to explain observed peculiarities of power density spectra of mass accretion rate variation of LMXB with long orbital period (Gilfanov, Arefiev, 2005).

12 - Stringent magnetic fields and early universe dynamos in cosmology with torsion

Garcia de Andrade

Cosmological magnetic seed fields of 10^{-32}G able to seed galactic dynamos are found by using Einstein-Cartan cosmology, possibility of confirming this result and improving it using brane H torsion is discussed.

13 - Differentiation of Active Galaxies Narrow lines to from BPT Diagrams

Juanita Torres

Classification of active galaxies is made through careful analysis of their spectra, either by measuring the width of the emission lines or comparing the flux ratios between these lines. One of the best known methods for this process are BPT (Baldwin, Phillips, & Terlevich) diagrams which allow the distinction of different types of active galaxies. In this article we present the study of a sample of active galaxies with thin lines taken from the SDSS (Sloan Digital Sky Survey) whose flux ratios were measured and diagnostic diagrams were constructed, thus allowing the differentiation between starburst (or HII) galaxies and authentic type 2 active galactic nuclei (AGNs). We show that there are some objects with similar spectra that have been misclassified.

14 - Magnetic Fields Signatures in Sun-Like Planet Hosting Stars

Julián David Alvarado-Gómez

Using a set of spectro-polarimetric observations we show a time-series of magnetic fields signatures in two Sun-like planet hosting stars, namely HD 1237 and HD 147513, via the Stokes I and V profiles. Applying Least Squares Deconvolution (LSD) techniques we have successfully detected magnetic field signatures in stars with different magnetic activity levels. In this initial study longitudinal field measurements and activity diagnostics are presented and used to search for a more precise rotation period and characterise the magnetic fields of these stars. The ultimate aim is to invert these Stokes I and V profiles to recover the large-scale magnetic fields in these stars and use these to understand the stellar environment around young planet forming systems.

15 - 3D Global Simulations of Turbulence and Dynamo Action in Magnetized Couette Flow

Krista Martocci

We present numerical evidence for large-scale dynamo action in a rotating disk. The results are from our three-dimensional, global simulations of magnetized cylindrical Taylor-Couette flow at high Reynolds numbers. The rotation profile of our set up is hydrodynamically stable, but hydromagnetically unstable. Therefore, only if a disk is magnetized will drive turbulence, which is necessary for efficient angular momentum transport. This leads to the question of whether these unstable disks can self magnetize or sustain dynamo action. In other words, can this turbulence generate and increase the magnetic fields necessary to continue driving the turbulence? The nonlinear evolution of the system leads to a sustained turbulent state capable of generating strong, coherent azimuthal magnetic structures. Cyclic behavior, in which these structures are formed and destroyed, is apparent in the simulations. The Maxwell stresses associated with the magnetic structures are largely responsible for the outward transport of angular momentum. We will discuss how this turbulent transport is affected by changes in the geometry, in particular, flattening to a more disk-like shape.

16 - Strong linear polarization detected in the cool active star II Peg

Lisa Rosén

Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy. The reliability of the maps can be improved if linear polarization is included in the reconstruction since linear polarization is sensitive to the transverse component of the magnetic field. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn stars, II Peg, HR 1099, IM Peg, and sigma Gem were observed at the CFHT. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Linear polarization was successfully detected in all four stars and II Peg showed an extraordinarily strong linear polarization signature. We therefore performed more observations of II Peg and have managed to obtain the first systematic observations of a cool star in all four Stokes parameters covering 12 rotational phases.

17 - Calculation of thermal conductivity coefficients for magnetized neutron star

M. V. Glushikhina

The coefficients that determine the electron heat transfer and diffusion in the crust of neutron stars are calculated on the basis of a solution of the Boltzmann equation with allowance for degeneracy.

18 - IGM Heating in Fossil Galaxy Groups

Miraghaei

Fossil galaxy groups famed to have undisturbed inter galactic gas by having no recent major mergers are energetically and morphologically perfect places to study IGM heating. In this work we investigated heating roles of active galactic nuclei in a sample of five known fossil galaxy groups using their GMRT observations in 610 MHz and 1.4 GHz. Radio lobes are detected for two fossil groups in the sample. We evaluated the PV work of the radio lobes and their corresponding heating powers in order to be compared with X-ray loss within cooling radius. Our results show heating powers is not sufficiently high to suppress the cooling. We also considered shock and vortex heating and conduction as complementary heating sources.

19 - the misterious nature of the magnetic ghost

Myself

This is so misterious that I cannot mention it

20 - Magnetic fields of Ap stars from the full Stokes vector spectropolarimetric observations

N. Rusomarov

Current knowledge about stellar magnetic fields relies almost entirely on circular polarization observations. Few objects have been observed in all four Stokes parameters. The magnetic Ap star HD24712 (DO Eri, HR1217) was recently observed in the Stokes IQUV parameters with the HARPSpol instrument at the 3.6-m ESO telescope. The resulting spectra have dense phase coverage, resolving power > 100000, and S/N ratio of 300-600. These are the highest quality full Stokes observations obtained for any star other than the Sun. We present preliminary results from magnetic Doppler imaging of HD24712. This analysis is the first step towards obtaining detailed 3-D maps of magnetic fields and abundance structures for HD24712 and other Ap stars that we currently observe with HARPSpol.

21 - on the structure of ADAFs with toroidal magnetic field and wind

nassim beiranvand

The main aim of this paper is studying the effect of toroidal magnetic field on the structure of Advection-Dominated Accretion flows (ADAF) in the presence of the turbulence viscosity and diffusivity duo to viscosity and magnetic field respectively. We use self-similar assumption in radial direction to solve the set of magnetohydrodynamic (MHD) equations for hot accretion disk. We adopt spherical coordinate $ (r, \theta, \varphi) $ to solve our equation. The toroidal component of magnetic field is considered and we also assumed that all three component of the velocity field are presented in our work, $ \mathbf{v}\equiv (v_{r}, v_{\theta}, v_{\varphi}) $. Then the equation reduce to a set of OEDs about $ \theta $ direction. To solve them, we put our symmetric boundary condition at the equatorial plane of the disk. Duo to these assumption, our results show that the radial velocity of the flow material will change its value to positive. So according to previous work by Jiao \& Wu 2011 we can define three region. The first region called inflow region. In this area, velocity has the negative value which started from midplane of the disk to certain inclination $ \theta_0 $, where $ v_{r}(\theta_{0}) = 0 $. It is obvious that at the inflow region, the accretion material moves toward the central object. Also the region that the $ v_{r}(\theta) > 0 $, is called outflow region which is placed between $ \theta_{0} $ and surface of the disk, $ \theta_{0} < \theta < \theta_{s} $, that the accretion flow moves away from the central object. At last by our configuration, the region between surface of the disk to polar axis is called wind region. This region will be vary small and the material blow out the surface in the form of wind.

22 - Fluctuation dynamo and their Faraday rotation signatures.

Pallavi Bhat

Turbulence is ubiquitous in many astrophysical systems like galaxies, galaxy clusters and possibly even the filaments in the intergalactic medium. We study fluctuation dynamo action in turbulent systems focusing on one observational signature; the ran- dom Faraday rotation measure (RM) from radio emission of background sources seen through the intermittent magnetic field generated by such a dynamo. We simulate the fluctuation dynamo in periodic boxes up to resolutions of $512^3$, with varying fluid and magnetic Reynolds numbers, and measure the resulting random RMs. We show that, even though the magnetic field generated is intermittent, it still allows for con- tributions to the RM to be significant. When the dynamo saturates, the rms value of RM is of order 40-50\% of the value expected in a model where fields of strength Brms uniformly fill cells of the largest turbulent eddy but are randomly oriented from one cell to another. This level of RM dispersion obtains across different values of mag- netic Reynolds number and Prandtl number explored. We also use the random RMs to probe the structure of the generated fields to distinguish the contribution from intense and diffuse field regions. We find that the strong field regions (say with B > 2Brms) contribute only of order 15-20\% to the RM. Thus rare structures do not dominate the RM; rather the general \u2019sea\u2019 of volume filling fluctuating fields are the dominant contributors. We also show that the magnetic integral scale, L_{int}, which is directly related to the RM dispersion, increases in all the runs, as Lorentz forces become important to saturate the dynamo. It appears that due to the ordering effect of the Lorentz forces, L_{int} of the saturated field tends to a modest fraction, 1/2\u22121/3 of the integral scale of the velocity field, for all our runs. These results are then applied to discuss the Faraday rotation signatures of fluctuation dynamo generated fields in young galaxies, galaxy clusters and intergalactic filaments.

23 - Observing Magnetic Activity with CHARA and Kepler

Rachael M. Roettenbacher

The observations of stellar magnetic activity have entered a new era with the sub-milliarcsecond resolving capabilities of the CHARA Array and the precise, nearly-continuous photometry from the Kepler satellite. We present "directly" imaged starspots from the CHARA Array, the world's largest infrared interferometer, and a comparison of contemporaneous Doppler and light-curve inversion images. Additionally, we present the first results from our Kepler Guest Observer Program, where our studies have revealed differential rotation, possible of magnetic activity cycles, and limits on spin-orbit misalignment. With the analysis of our full dataset, we will reveal unprecedented detail in the relations between stellar age and spectral type on surface magnetic activity.

24 - Molecules and the Magnetohydrostatic Equilibrium in Sunspots

Sarah A. Jaeggli

The atmosphere in sunspot umbrae provides a cool environment where many species of simple of molecules can form. Typically, the molecular populations are insignificant compared to the atomic gas and are unable to change the physical properties of the atmosphere. In the case of molecular hydrogen (H$_2$), previous modeling efforts have shown that large populations ($\sim10\%$) are able to form at umbral temperatures. Such a large molecular population has several interesting implications, and also provides a mechanism for rapidly concentrating the umbral magnetic field during the initial formation of sunspots and during their decay. We have explored the magnetohydrostatic equilibrium in sunspots over a wide range of sizes and evolutionary states based on observations of a large sample of sunspots obtained over two years using the Facility InfraRed Spectropolarimter on the Dunn Solar Telescope. Magnetic fields were characterized by Milne-Eddington inversion of the highly sensitive 1565 nm Zeeman-split Fe I lines, and observed OH line strengths at the same wavelength were established as a proxy for H$_2$ based on spectral synthesis of umbral atmospheric models. Isothermal increases in the magnetic field strength seen in some sunspots are found to correspond well with large OH strengths, indicating the growth or decay of a large H$_2$ population.