bluuebunny/crossref_metadata_2025 huggingface dataset:
The Image of Turkey in Europe Today
Authors: Haller Max
Published: July 2013

The relations between different countries and continents have always been important politically and scientifically. This applies in particular to relations between Turkey and Europe. Through centuries, the Ottoman Empire was seen as the main enemy of ‘Christian Europe’. In this paper, three topics are discussed: (1) European, and in particular Austrian and German, attitudes towards Turkey's membership in the European Union. It is argued that the dominantly negative attitudes in this regard do not indicate a generally negative attitude towards Turkey. (2) Some of the reasons for the negative view of Turkish EU-membership in many EU countries are discussed. (3) In conclusion, three issues are taken up: the relevance of Turkish EU-membership; the reasons and persistence of national and ethnic stereotypes; the relevance of the time factor in international relations.
Core–Periphery Interactions in the Late and Post-Ottoman Periods: Dependency and the Uneven Development of Thessaloniki: 1870–1936
Authors: Srougo Shai
Published: July 2013

What are the reasons for the rapid economic growth of regions and their later decline? Why does the development of a certain region create under-development in another region within a national or global sphere? A central paradigm for explaining such phenomena is core–periphery relations, and the case study presented in this paper is the port city of Thessaloniki and its regressive and peripheral status within the regional (Macedonia and the Southern Balkans), national (State of Greece), and international (the capitalist world- system) spheres during two main political periods: (i) the final decades of the Ottoman regime in Macedonia (1870–1912); (ii) the first quarter of a century in which Thessaloniki integrated with Greece (1912–1936).
Mechanism of action of ketamine
Authors: Stahl Stephen M.
Published: July 2013

ISSUE:Ketamine induces rapid-onset and short-duration improvement in depressive and suicidal symptoms in both treatment-resistant unipolar depression and bipolar depression, and also reduces chronic pain after short intravenous infusions. In order to develop long-acting oral agents with the same clinical effects, the pharmacologic mechanism of action must be understood, and the leading hypotheses are discussed here.
Cognition in Early Relapsing-Remitting Multiple Sclerosis: Consequences May Be Relative to Working Memory
Authors: Berrigan Lindsay I. , LeFevre Jo-Anne , Rees Laura M. , Berard Jason , Freedman Mark S. , Walker Lisa A.S.
Published: July 2013

The Relative Consequence Model proposes multiple sclerosis (MS) patients have a fundamental deficit in processing speed that compromises other cognitive functions. The present study examined the mediating role of processing speed, as well as working memory, in the MS-related effects on other cognitive functions for early relapsing-remitting patients. Seventy relapsing-remitting MS patients with disease duration not greater than 10 years and 72 controls completed tasks assessing processing speed, working memory, learning, and executive functioning. The possible mediating roles of speed and working memory in the MS-related effects on other cognitive functions were evaluated using structural equation modeling. Processing speed was not significantly related to group membership and could not have a mediating role. Working memory was related to group membership and functioned as a mediating/intervening factor. The results do not support the Relative Consequence Model in this sample and they challenge the notion that working memory impairment only emerges at later disease stages. The results do support a mediating/intervening role of working memory. These results were obtained for early relapsing-remitting MS patients and should not be generalized to the broader MS population. Instead, future research should examine the relations that exist at other disease stages. (JINS, 2013, 19, 1–12)
Quantifying Cognitive Reserve in Older Adults by Decomposing Episodic Memory Variance: Replication and Extension
Authors: Zahodne Laura B. , Manly Jennifer J. , Brickman Adam M. , Siedlecki Karen L. , DeCarli Charles , Stern Yaakov
Published: July 2013

The theory of cognitive reserve attempts to explain why some individuals are more resilient to age-related brain pathology. Efforts to explore reserve have been hindered by measurement difficulties. Reed et al. (2010) proposed quantifying reserve as residual variance in episodic memory performance that remains after accounting for demographic factors and brain pathology (whole brain, hippocampal, and white matter hyperintensity volumes). This residual variance represents the discrepancy between an individual's predicted and actual memory performance. The goals of the present study were to extend these methods to a larger, community-based sample and to investigate whether the residual reserve variable is explained by age, predicts longitudinal changes in language, and predicts dementia conversion independent of age. Results support this operational measure of reserve. The residual reserve variable was associated with higher reading ability, lower likelihood of meeting criteria for mild cognitive impairment, lower odds of dementia conversion independent of age, and less decline in language abilities over 3 years. Finally, the residual reserve variable moderated the negative impact of memory variance explained by brain pathology on language decline. This method has the potential to facilitate research on the mechanisms of cognitive reserve and the efficacy of interventions designed to impart reserve. (JINS, 2013, 19, 1–9)
Serum ferritin contributes to racial or geographic disparities in metabolic syndrome in Taiwan
Authors: Chang Jung-Su , Lin Shiue-Ming , Chao Jane C-J , Chen Yi-Chun , Wang Chi-Mei , Chou Ni-Hsin , Pan Wen-Harn , Bai Chyi-Huey
Published: July 2013

Objectives

Asians and Pacific Islanders have higher circulating serum ferritin (SF) compared with Caucasians but the clinical significance of this is unclear. There is a higher prevalence of metabolic syndrome (MetS) in Taiwanese Indigenous than Han Chinese. Genetically, Indigenous are related to Austronesians and account for 2 % of Taiwan's population. We tested the hypothesis that accumulation of Fe in the body contributes to the ethnic/racial disparities in MetS in Taiwan.

Design

A population-based, cross-sectional study.

Setting

National Nutrition and Health Survey in Taiwan and Penghu Island.

Subjects

A total of 2638 healthy adults aged ≥19 years. Three ethnic groups were included.

Results

Han Chinese and Indigenous people had comparable levels of SF. Austronesia origin was independently associated with MetS (OR = 2·61, 95 % CI 2·02, 3·36). After multiple adjustments, the odds for MetS (OR = 2·49, 95 % CI 1·15, 5·28) was significantly higher among Indigenous people in the highest SF tertile compared with those in the lowest tertile. Hakka and Penghu Islanders yielded the lowest risks (OR = 1·08, 95 % CI 0·44, 2·65 and OR = 1·21, 95 % CI 0·52, 2·78, respectively). Indigenous people in the highest SF tertile had increased risk for abnormal levels of fasting glucose (OR = 2·34, 95 % CI 1·27, 4·29), TAG (OR = 1·94, 95 % CI 1·11, 3·39) and HDL-cholesterol (OR = 2·10, 95 % CI 1·18, 3·73) than those in the lowest SF tertile.

Conclusions

Our results raise the possibility that ethnic/racial differences in body Fe store susceptibility may contribute to racial and geographic disparities in MetS.
Macronutrient intake and type 2 diabetes risk in middle-aged Australian women. Results from the Australian Longitudinal Study on Women's Health
Authors: Alhazmi Amani , Stojanovski Elizabeth , McEvoy Mark , Garg Manohar L
Published: July 2013

Objective

To investigate the association between macronutrient intake and type 2 diabetes risk in middle-aged Australian women.

Design

A prospective cohort study, with 6 years (2002–2007) of follow up. Dietary intake was assessed with a validated FFQ. Relative risks with 95 % confidence intervals were used to examine risk associations.

Setting

Australian Longitudinal Study on Women's Health, Australia.

Subjects

Australian women (n 8370) from the Australian Longitudinal Study on Women's Health aged 45–50 years and free of type 2 diabetes at baseline.

Results

After 6 years of follow-up, 311 women developed type 2 diabetes. After adjusting for sociodemographic, lifestyle and other dietary risk factors, MUFA, total n-3 PUFA, α-linolenic acid and total n-6 PUFA intakes were positively associated with the incidence of type 2 diabetes. The relative risks for type 2 diabetes for the highest compared with the lowest quintiles were 1·64 (95 % CI 1·06, 2·54), P = 0·04 for MUFA; 1·55 (95 % CI 1·03, 2·32), P = 0·01 for n-3 PUFA; 1·84 (95 % CI 1·25, 2·71), P < 0·01 for α-linolenic acid; and 1·60 (95 % CI 1·03, 2·48), P = 0·04 for n-6 PUFA. Other dietary macronutrients were not significantly associated with diabetes risk.

Conclusions

The data indicate that consumption of MUFA, n-3 PUFA and n-6 PUFA may influence the risk of developing type 2 diabetes in women.
BALANCE FOR TATE COHOMOLOGY WITH RESPECT TO SEMIDUALIZING MODULES
Authors: LIANG LI , YANG GANG
Published: July 2013

In this paper, we further study Tate cohomology of modules over a commutative ring with respect to semidualizing modules using the ideals of Sather-Wagstaff et al. [‘Tate cohomology with respect to semidualizing modules’, J. Algebra 324 (2010), 2336–2368]. In particular, we prove a balance result for the Tate cohomology ${\widehat{\mathrm{Ext} }}^{n} $ for any $n\in \mathbb{Z} $. This result complements the work of Sather-Wagstaff et al., who proved that the result holds for any $n\geq 1$. We also discuss some vanishing properties of Tate cohomology.
Microlocal Euler classes and Hochschild homology
Authors: Kashiwara Masaki , Schapira Pierre
Published: July 2013

We define the notion of a trace kernel on a manifold $M$. Roughly speaking, it is a sheaf on $M\times M$ for which the formalism of Hochschild homology applies. We
associate a microlocal Euler class with such a kernel, a cohomology class with values
in the relative dualizing complex of the cotangent bundle ${T}^{\ast } M$ over $M$, and we prove that this class is functorial with respect to the
composition of kernels.

This generalizes, unifies and simplifies various results from (relative) index
theorems for constructible sheaves, $\mathscr{D}$-modules and elliptic pairs.
Unipotent differential algebraic groups as parameterized differential Galois groups
Authors: Minchenko Andrey , Ovchinnikov Alexey , Singer Michael F.
Published: July 2013

We deal with aspects of direct and inverse problems in parameterized Picard–Vessiot (PPV) theory. It is known that, for certain fields, a linear differential algebraic group (LDAG)$G$is a PPV Galois group over these fields if and only if$G$contains a Kolchin-dense finitely generated group. We show that, for a class of LDAGs$G$, including unipotent groups,$G$is such a group if and only if it has differential type$0$. We give a procedure to determine if a parameterized linear differential equation has a PPV Galois group in this class and show how one can calculate the PPV Galois group of a parameterized linear differential equation if its Galois group has differential type$0$.
Flux-transport and mean-field dynamo theories of solar cycles
Authors: Choudhuri Arnab Rai
Published: July 2013

We point out the difficulties in carrying out direct numerical simulation of the solar dynamo problem and argue that kinematic mean-field models are our best theoretical tools at present for explaining various aspects of the solar cycle in detail. The most promising kinematic mean-field model is the flux transport dynamo model, in which the toroidal field is produced by differential rotation in the tachocline, the poloidal field is produced by the Babcock–Leighton mechanism at the solar surface and the meridional circulation plays a crucial role. Depending on whether the diffusivity is high or low, either the diffusivity or the meridional circulation provides the main transport mechanism for the poloidal field to reach the bottom of the convection zone from the top. We point out that the high-diffusivity flux transport dynamo model is consistent with various aspects of observational data. The irregularities of the solar cycle are primarily produced by fluctuations in the Babcock–Leighton mechanism and in the meridional circulation. We summarize recent work on the fluctuations of meridional circulation in the flux transport dynamo, leading to explanations of such things as the Waldmeier effect.
Solar-cycle precursors and predictions
Authors: Jiang Jie
Published: July 2013

The sunspot number data during the past 400 years indicates that both the profile and the amplitude of the solar cycle have large variations. Some precursors of the solar cycle were identified aiming to predict the solar cycle. The polar field and the geomagnetic index are two precursors which are received the most attention. The geomagnetic variations during the solar minima are potentially caused by the solar polar field by the connection of the solar open flux. The robust prediction skill of the polar field indicates that the memory of the dynamo process is less than 11 yrs based on the frame of the Babcock-Leighton flux transport dynamo. One possible reason to get the short magnetic memory is the high magnetic diffusivity in the convective zone. Our recent studies show that the radial downward pumping is another possible reason. Based upon the mechanism, we well simulate the cycle irregularities during RGO time period. This opens the possibility to set up a standard dynamo based model to predict the solar cycle. In the end, the no correlation between the polar field and the preceding cycle strength due to two nonlinearities involved in the sunspot emergence will be stressed.
Digitization of Spörer's sunspot drawings
Authors: Diercke Andrea , Arlt Rainer , Denker Carsten
Published: July 2013

Much of our knowledge about the solar dynamo is based on sunspot observations. It is thus desirable to extend the set of positional and morphological data of sunspots into the past. Gustav Spörer observed in Germany from Anklam (1861–1873) and Potsdam (1874–1894). He left detailed prints of sunspot groups, which we digitized and processed to mitigate artifacts left in the print by the passage of time. After careful geometrical correction, the sunspot data are now available as synoptic charts for almost 450 solar rotation periods. Individual sunspot positions can thus be precisely determined and spot areas can be accurately measured using morphological image processing techniques. These methods also allow us to determine tilt angles of active regions (Joy's law) and to assess the complexity of an active region.
Dependence of solar cycles duration on the magnitude of the annual module of the sunspots magnetic field
Authors: Krivodubskij Valery N. , Lozitska Natalia I.
Published: July 2013

The dependence of the solar cycle duration, T, on the 3 years averaged module of the large-scale sunspots magnetic fields (30-60 arcsec), Bsp index, was investigated on the base of about 10,000 visual observations conducted during last eight (16-23) cycles. It was found that the duration T of the investigated cycles linearly depends on the index Bsp of the magnetic fields observed during 3 years on decline phase of the solar cycle (second, third and fourth years after solar maximum Tmax). Namely, the duration of the cycles T was varied between 9,5 and 12,5 years, when the magnetic index Bsp was ranged from 2450 to 2600 G. An explanation for this dependence is proposed within the framework of non-linear αΩ- dynamo model. We found the following equation for the dependence of solar dynamo-period on magnetic index: T ≈ Bsp3/2. Therefore, the large observed index Bsp, the longer calculated period T.
Solar cycle and quasi-biennial variations in helioseismic frequencies
Authors: Tripathy Sushanta C. , Jain Kiran , Simoniello Rosaria , Hill Frank , Turck-Chièze Sylvaine
Published: July 2013

The prolonged period of solar minimum between cycles 23 and 24 has invoked a great deal of interest to understand the origin of the unusually low solar activity. Even though the origin of solar activity is believed to lie in the shear layer at the base of the convection zone, the analysis of helioseismic data seem to orientate us toward the near surface. In this context, we analyze the signature of the quasi-biennial periodicity seen in the oscillation frequencies which may provide additional constraints on the solar dynamo models.
Interplanetary scintillation signatures in the inner heliosphere of the deepest solar minimum in the past 100 years
Authors: Bisoi Susanta Kumar , Janardhan P.
Published: July 2013

We have used interplanetary scintillation (IPS) observations at 327 MHz spanning years 1983-2009 to study microturbulence levels in the inner heliosphere. We find that the microturbulence levels show a steady and significant drop in the entire inner heliosphere starting from around 1995. The fact that the solar polar fields have also shown a similar declining trend provides a consistent result showing the buildup to the solar minimum between the solar cycles 23 and 24, the deepest in the past 100 years, actually began more than a decade earlier.
Asymmetry in the periodicities of solar photospheric fields: A probe to the unusual solar minimum prior to cycle 24
Authors: Bisoi Susanta Kumar , Janardhan P.
Published: July 2013

Employing wavelet and Fourier methods, we investigate temporal variations of periodicities in the photospheric fields obtained from synoptic magnetograms of the National Solar Observatory at Kitt Peak (NSO/KP) spanning the years 1975-2009. A north-south asymmetry is noticed in the periodicities of photospheric fields in the latitude range, 45°-78°, when the data is grouped into fields prior to and after 1996. This asymmetry when coupled with the fact that both solar fields in the latitude range, 45°-78°, and the micro-turbulence levels in the inner heliosphere began declining ~ 1995-1996 suggests that active changes occurred in the underlying basic solar processes which eventually initiated, at the end of solar cycle 23, the build-up of the deepest solar minimum, in the past 100 years.
Solar magneto-convection
Authors: Schüssler Manfred
Published: July 2013

An overview is given about recent developments and results of comprehensive simulations of magneto-convective processes in the near-surface layers and photosphere of the Sun. Simulations now cover a wide range of phenomena, from whole active regions, over individual sunspots and pores, magnetic flux concentrations and vortices in intergranular lanes, down to the intricate mixed-polarity structure of the magnetic field generated by small-scale dynamo action. The simulations in concert with high-resolution observations have provided breakthroughs in our understanding of the structure and dynamics of the magnetic fields in the solar photosphere.
Solar cycle variation of helicity characteristics indicated by SP/Hinode
Authors: Hao Juan , Zhang Mei
Published: July 2013

Helicity characteristics in active regions (ARs) are studied, using so far the most accurate vector magnetic field measurements obtained with SP/Hinode. Our sample includes all ARs observed by SP/Hinode, up to June 2012. The sample is divided into three sub-samples: Cycle 23 (from 2006.11 to 2008.06), Cycle 24a (from 2008.10 to 2010.09) and Cycle 24b (from 2010.10 to 2012.06). We confirm our previous findings that the usual hemispheric helicity sign rule is not obeyed in the descending phase of solar cycle 23 and is obeyed in the ascending phase of solar cycle 24. And we find that the second phase of the solar cycle 24 (Cycle 24b) shows an even stronger evidence of the usual hemispheric helicity sign rule than its first phase (Cycle 24a). It is also found that our previous finding that the strong and weak fields possess the opposite helicity signs is not followed in Cycle 24b, whereas it is weakly followed in Cycle 24a and strongly followed in the descending phase of Cycle 23. This means that this rule also has a solar cycle variation, in addition to the solar cycle variation of the usual hemispheric helicity sign rule, and there is a roughly 2-years time delay between the two.
Role of longitudinal activity complexes for solar and stellar dynamos
Authors: Mantere Maarit J. , Käpylä Petri J. , Pelt Jaan
Published: July 2013

In this paper we first discuss observational evidence of longitudinal concentrations of magnetic activity in the Sun and rapidly rotating late-type stars with outer convective envelopes. Scenarios arising from the idea of rotationally influenced anisotropic convective turbulence being the key physical process generating these structures are then presented and discussed - such effects include the turbulent dynamo mechanism, negative effective magnetic pressure instability (NEMPI) and hydrodynamical vortex instability. Finally, we discuss non-axisymmetric stellar mean-field dynamo models, the results obtained with them, and compare those with the observational information gathered up so far. We also present results from a pure α2 mean-field dynamo model, which show that time-dependent behavior of the dynamo solutions can occur both in the form of an azimuthal dynamo wave and/or oscillatory behavior related to the alternating energy levels of the active longitudes.
The gap of differential rotation in early F-type stars
Authors: Eiff Matthias Ammler-von , Reiners Ansgar
Published: July 2013

We present new measurements of the rotational profile of 56 nearby stars of spectral types A-F obtained by line profile analysis. Together with earlier work, we now know of 33 stars in which Sun-like differential rotation was identified by line profile analysis. We find evidence of two populations of differential rotators, one group of rapidly rotating A stars at the granulation boundary with strong horizontal shear, and another group of mid- to late-F type stars with moderate rates of rotation and less shear. There is a gap between A and F stars, in which the stars appear to exhibit very little shear. Apparently, the physical conditions of differential rotation change at early-F spectral types.
A nonextensive approach for the angular momentum loss rate in low-mass stars
Authors: de Freitas Daniel B. , De Medeiros J. R.
Published: July 2013

The present study demonstrates that behavior of rotational velocity as a function of stellar age is consistent using Tsallis' nonextensive formalism, resulting in a new approach to understanding the stellar rotational scenario.
CoRot observation of a young Sun-like star
Authors: Gondoin P. , Gandolfi D. , Fridlund M. , Guenther E. W. , Hatzes A.
Published: July 2013

The present study reports measurements of the rotation period of a young solar analogue, estimates of its surface coverage by photospheric starspots and of its chromospheric activity level, and derivations of its evolutionary status. It compares the chromospheric activity level of this young star with a model of chromospheric activity evolution established by combining relationships between the R′HK index and the Rossby number with a recent model of stellar rotation evolution on the main-sequence.
Magnetic activity and solar-like pulsations of X-ray sources in the Kepler field of view
Authors: Molenda-Żakowicz Joanna , Frasca Antonio , Fröhlich Hans-Erich
Published: July 2013

We report on cross-matching the ROSAT All-Sky Survey and the XMM-Newton catalogs with the Kepler Input Catalog (KIC). For several stars associated with X-ray sources, we provide also an access to our high-resolution spectroscopic observations.
Magnetic fields in our Milky Way Galaxy and nearby galaxies
Authors: Han JinLin
Published: July 2013

Magnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, polarized emission from dust grains and clouds at millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or maser lines from clouds or clumps, diffuse radio synchrotron emission from relativistic electrons in interstellar magnetic fields, and the Faraday rotation of background radio sources as well as pulsars for our Milky Way. It is easy to get a global structure for magnetic fields in nearby galaxies, while we have observed many details of magnetic fields in our Milky Way, especially by using pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large-scale structure as toroidal and poloidal fields, but seem to be slightly weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as vertical components. Magnetic field directions in galaxies seem to have been preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds and then to the cloud cores in star formation regions or clumps for the maser spots. Magnetic fields in galaxies are passive to dynamics.
Interstellar and intergalactic dynamos
Authors: Hanasz M. , Woltanski D. , Kowalik K.
Published: July 2013

We review recent developments of amplification models of galactic and intergalactic magnetic field. The most popular scenarios involve variety of physical mechanisms, including turbulence generation on a wide range of physical scales, effects of supernovae, buoyancy as well as the magnetorotational instability. Other models rely on galaxy interaction, which generate galactic and intergalactic magnetic fields during galaxy mergers. We present also global galactic-scale numerical models of the Cosmic Ray (CR) driven dynamo, which was originally proposed by Parker (1992). We conduct a series of direct CR+MHD numerical simulations of the dynamics of the interstellar medium (ISM), composed of gas, magnetic fields and CR components. We take into account CRs accelerated in randomly distributed supernova (SN) remnants, and assume that SNe deposit small-scale, randomly oriented, dipolar magnetic fields into the ISM. The amplification timescale of the large-scale magnetic field resulting from the CR-driven dynamo is comparable to the galactic rotation period. The process efficiently converts small-scale magnetic fields of SN-remnants into galactic-scale magnetic fields. The resulting magnetic field structure resembles the X-shaped magnetic fields observed in edge-on galaxies.
Small-scale dynamo action in primordial halos
Authors: Schober Jennifer , Schleicher Dominik R. G. , Klessen Ralf S. , Federrath Christoph , Bovino Stefano , Glover Simon , Banerjee Robi
Published: July 2013

The first galaxies form due to gravitational collapse of primordial halos. During this collapse, weak magnetic seed fields get amplified exponentially by the small-scale dynamo - a process converting kinetic energy from turbulence into magnetic energy. We use the Kazantsev theory, which describes the small-scale dynamo analytically, to study magnetic field amplification for different turbulent velocity correlation functions. For incompressible turbulence (Kolmogorov turbulence), we find that the growth rate is proportional to the square root of the hydrodynamic Reynolds number, Re1/2. In the case of highly compressible turbulence (Burgers turbulence) the growth rate increases proportional to Re1/3. With a detailed chemical network we are able to follow the chemical evolution and determine the kinetic and magnetic viscosities (due to Ohmic and ambipolar diffusion) during the collapse of the halo. This way, we can calculate the growth rate of the small-scale dynamo quantitatively and predict the evolution of the small-scale magnetic field. As the magnetic energy is transported to larger scales on the local eddy-timescale, we obtain an estimate for the magnetic field on the Jeans scale. Even there, we find that equipartition with the kinetic energy is reached on small timescales. Dynamically relevant field structures can thus be expected already during the formation of the first objects in the Universe.
Mechanisms of formation ofsolar pores and sunspots
Authors: Kitiashvili Irina N.
Published: July 2013

Spontaneous formation of self-organized magnetic structures, such as sunspots and pores, is one of intriguing and oldest problems, which represents a complicated interaction of convection and magnetic fields on different scales. Observations of sunspots and pores formation reveal a fast process of accumulation of emerging magnetic field into stable long-living magnetic structures. However, the physical mechanisms of the flux accumulation into the compact magnetic structures with high field strength and their stability are not clear. Development of observational capabilities, theory, and realistic-type MHD numerical simulations open a new level of our understanding of the turbulent processes of the magnetic field accumulation. I discuss the recent progress in observations and radiative MHD simulations that provide important clues for possible mechanisms of formation and stability of sunspots and pores, and their links to the dynamo process.
Flux concentrations in turbulent convection
Authors: Käpylä Petri J. , Brandenburg Axel , Kleeorin Nathan , Mantere Maarit J. , Rogachevskii Igor
Published: July 2013

We present preliminary results from high resolution magneto-convection simulations where we find the formation of flux concentrations from an initially uniform magnetic field. The structures appear in roughly ten convective turnover times and live close to a turbulent diffusion time. The time scales are compatible with the negative effective magnetic pressure instability (NEMPI), although structure formation is not restricted to regions where the effective magnetic pressure is negative.
Fractal multi-scale nature of solar/stellar magnetic fields
Authors: Abramenko Valentina I.
Published: July 2013

An abstract mathematical concept of fractal organization of certain complex objects received significant attention in astrophysics during last decades. The concept evolved into a broad field including multi-fractality and intermittency, percolation theory, self-organized criticality, theory of catastrophes, etc. Such a strong mathematical and physical approach provide new possibilities for exploring various aspects of astrophysics. In particular, in the solar and stellar magnetism, multi-fractal properties of magnetized plasma turned to be useful for understanding burst-like dynamics of energy release events, conditions for turbulent dynamo action, nature of turbulent magnetic diffusivity, and even the dual nature of solar dynamo. In this talk, I will briefly outline how the ideas of multi-fractality are used to explore the above mentioned aspects of solar magnetism.
Solar-like differential rotation and equatorward migration in a convective dynamo with a coronal envelope
Authors: Warnecke J. , Käpylä P. J. , Mantere M. J. , Brandenburg A.
Published: July 2013

We present results of convective turbulent dynamo simulations including a coronal layer in a spherical wedge. We find an equatorward migration of the radial and azimuthal fields similar to the behavior of sunspots during the solar cycle. The migration of the field coexist with a spoke-like differential rotation and anti-solar (clockwise) meridional circulation. Even though the migration extends over the whole convection zone, the mechanism causing this is not yet fully understood.
Magnetic helicity transported by flux emergence and shuffling motions
Authors: Zhang Y. , Kitai R. , Takizawa K.
Published: July 2013

Magnetic helicity can be transported from sub-photosphere into corona by the emergence of helical magnetic field lines and the shuffling motions of foot-points of pre-existing coronal field lines. Active region NOAA 10930 was observed by SP and NFI of SOT on board Hinode when it pass through the solar meridian. Based on these observations, we calculate magnetic helicity flow of both terms, by regarding Doppler velocity as normal velocity. The results are compared with which calculated by method proposed by Zhang et. al. (2012). Our results show that helicity injection maps calculated by both methods have similar distribution and the integration values have the same magnitude.
On magnetohydrodynamic turbulence and angular momentum transport in accretion disk boundary layers
Authors: Chan Chi-kwan , Pessah Martin E.
Published: July 2013

The physical modeling of the accretion disk boundary layer, the region where the disk meets the surface of the accreting star, usually relies on the assumption that angular momentum transport is opposite to the radial angular frequency gradient of the disk. The standard model for turbulent shear viscosity, widely adopted in astrophysics, satisfies this assumption by construction. However, this behavior is not supported by numerical simulations of turbulent magnetohydrodynamic (MHD) accretion disks, which show that angular momentum transport driven by the magnetorotational instability is inefficient in this inner disk region. I will discuss the results of a recent study on the generation of hydromagnetic stresses and energy density in the boundary layer around a weakly magnetized star. Our findings suggest that although magnetic energy density can be significantly amplified in this region, angular momentum transport is rather inefficient. This seems consistent with the results obtained in numerical simulations and suggests that the detailed structure of turbulent MHD boundary layers could differ appreciably from those derived within the standard framework of turbulent shear viscosity.
Toward understanding the multiscale spatial spectrum of solar convection
Authors: Getling A. V. , Mazhorova O. S. , Shcheritsa O. V.
Published: July 2013

Convection is simulated numerically based on two-dimensional Boussinesq equations for a fluid layer with a specially chosen stratification such that the convective instability is much stronger in a thin subsurface sublayer than in the remaining part of the layer. The developing convective flow has a small-scale component superposed onto a basic large-scale roll flow.
Helicity–vorticity turbulent pumping of magnetic fields in the solar dynamo
Authors: Pipin V. V.
Published: July 2013

The interaction of helical convective motions and differential rotation in the solar convection zone results in turbulent drift of a large-scale magnetic field. We discuss the pumping mechanism and its impact on the solar dynamo.
Non-linear and chaotic dynamo regimes
Authors: Brandenburg Axel
Published: July 2013

An update is given on the current status of solar and stellar dynamos. At present, it is still unclear why stellar cycle frequencies increase with rotation frequency in such a way that their ratio increases with stellar activity. The small-scale dynamo is expected to operate in spite of a small value of the magnetic Prandtl number in stars. Whether or not the global magnetic activity in stars is a shallow or deeply rooted phenomenon is another open question. Progress in demonstrating the presence and importance of magnetic helicity fluxes in dynamos is briefly reviewed, and finally the role of nonlocality is emphasized in modeling stellar dynamos using the mean-field approach. On the other hand, direct numerical simulations have now come to the point where the models show solar-like equatorward migration that can be compared with observations and that need to be understood theoretically.
Experimental realization of dynamo action: present status and prospects
Authors: Giesecke André , Stefani Frank , Gundrum Thomas , Gerbeth Gunter , Nore Caroline , Léorat Jacques
Published: July 2013

In the last decades, the experimental study of dynamo action has made great progress. However, after the dynamo experiments in Karlsruhe and Riga, the von-Kármán-Sodium (VKS) dynamo is only the third facility that has been able to demonstrate fluid flow driven self-generation of magnetic fields in a laboratory experiment. Further progress in the experimental examination of dynamo action is expected from the planned precession driven dynamo experiment that will be designed in the framework of the liquid sodium facility DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies).

In this paper, we briefly present numerical models of the VKS dynamo that demonstrate the close relation between the axisymmetric field observed in that experiment and the soft iron material used for the flow driving impellers. We further show recent results of preparatory water experiments and design studies related to the precession dynamo and delineate the scientific prospects for the final set-up.
Flux transport dynamo coupled with a fast tachocline scenario
Authors: Karak Bidya Binay , Petrovay Kristof
Published: July 2013

The tachocline is important in the solar dynamo for the generation and the storage of the magnetic fields. A most plausible explanation for the confinement of the tachocline is given by the fast tachocline model in which the tachocline is confined by the anisotropic momentum transfer by the Maxwell stress of the dynamo generated magnetic fields. We employ a flux transport dynamo model coupled with the simple feedback formula of this fast tachocline model which basically relates the thickness of the tachocline to the Maxwell stress. We find that this nonlinear coupling not only produces a stable solar-like dynamo solution but also a significant latitudinal variation in the tachocline thickness which is in agreement with the observations.
Solar dynamo model with nonlocal alpha-effect and diamagnetic pumping
Authors: Kitchatinov L. L. , Olemskoy S. V.
Published: July 2013

Sunspot data and large-scale solar magnetic field data are used to demonstrate the operation of the Babcock-Leighton mechanism on the Sun. A dynamo model is developed that employs jointly a nonlocal alpha-effect of the Babcock-Leighton type and diamagnetic downward pumping. The pumping concentrates magnetic fields to the base of the convection zone. The magnetic cycle period, equatorial symmetry of the generated fields, their meridional drift, and the polar-to-toroidal field ratio obtained in the model agree with observations.
Modelling stellar activity cycles using deep-seated dynamos and surface flux transport
Authors: Işık Emre , Schmitt Dieter , Schüssler Manfred
Published: July 2013

We investigate the relations between tachocline-based dynamos and the surface flux transport mechanisms in stars with outer convection zones. Using our combined models of flux generation and transport, we demonstrate the importance of the buoyant rise of magnetic flux, which physically determines the emergence latitudes and tilt angles of bipolar magnetic regions. The combined effects of the dynamo strength, flux rise, and surface transport lead to various cyclic and non-cyclic time series of total unsigned surface magnetic flux.
Forecasting the solar activity cycle: new insights
Authors: Nandy Dibyendu , Karak Bidya Binay
Published: July 2013

Having advance knowledge of solar activity is important because the Sun's magnetic output governs space weather and impacts technologies reliant on space. However, the irregular nature of the solar cycle makes solar activity predictions a challenging task. This is best achieved through appropriately constrained solar dynamo simulations and as such the first step towards predictions is to understand the underlying physics of the solar dynamo mechanism. In Babcock-Leighton type dynamo models, the poloidal field is generated near the solar surface whereas the toroidal field is generated in the solar interior. Therefore a finite time is necessary for the coupling of the spatially segregated source layers of the dynamo. This time delay introduces a memory in the dynamo mechanism which allows forecasting of future solar activity. Here we discuss how this forecasting ability of the solar cycle is affected by downward turbulent pumping of magnetic flux. With significant turbulent pumping the memory of the dynamo is severely degraded and thus long term prediction of the solar cycle is not possible; only a short term prediction of the next cycle peak may be possible based on observational data assimilation at the previous cycle minimum.
CrH molecule: New diagnostic tool for measuring magnetic fields of cool dwarfs
Authors: Kuzmychov Oleksii , Berdyugina Svetlana V.
Published: July 2013

The quantum mechanical calculations for the A6Σ+ − X6Σ+ system of the CrH molecule were done in order to obtain its energy level structure and transition strenghts both in the absence and in the presence of a magnetic field. Employing this results and solving a set of the radiative transfer equations, we calculated the Stokes profiles for the entire 0-0 band for different magnetic field strengths and orientations. We show that the CrH lines produce a considerable polarization signal (up to 20%) at 0.5 - 10 kG. Furthermore, the polarization signal shows a significant asymmetry (broad-band polarization) that arises from the Paschen-Back effect in the individual CrH lines. An example of the signal, as it can be observed, is provided.
Venus transit, aureole and solar diameter
Authors: Xie Wenbin , Sigismondi Costantino , Wang Xiaofan , Tanga Paolo
Published: July 2013

The possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.
Radio imaging-spectroscopy observations of the Sun in decimetric and centimetric wavelengths
Authors: Yan Yihua , Wang Wei , Liu Fei , Geng Lihong , Chen Zhijun , Zhang Jian
Published: July 2013

To address fundamental processes in the solar eruptive phenomena it is important to have imaging-spectroscopy over centimetric-decimetric wave range. The Chinese Spectral Radioheliograph (CSRH) in 0.4-15 GHz range with high time, space and frequency resolutions is being constructed to achieve this goal. The perspectives to open new observational windows on solar flares and CMEs will be achieved by mapping the radio emission from unstable electron populations during the basic processes of energy release. CSRH is located in a radio quiet region in Inner Mongolia of China. The array of CSRH-I in 0.4-2.0 GHz with 40 4.5m antennas has been established and starts test observations. The 60 2m antennas for array of CSRH-II in 2-15 GHz have been mounted and assembled. The progress and current status of CSRH are introduced.
Calibration and data analysis for Chinese Spectral Radioheliograph
Authors: Wang W. , Yan Y. H. , Liu D. H. , Chen Z. J. , Liu F. , Geng L. H. , Chen L. J. , Su C.
Published: July 2013

The Chinese Spectral Radioheliograph (CSRH) is under construction in Mingantu station of NAOC in China. Now, CSRH-I which includes antenna, receiver and correlator in decimetric wave range has been established. This paper introduced calibration on CSRH and present some results of data processing.
Micorwave observations of the Chinese Solar Broadband Radio Spectrometer at Huairou
Authors: Tan Chengming , Tan Baolin , Yan Yihua , Liu Yuying
Published: July 2013

This work presents an overview of the microwave observations of the Chinese Solar Broadband Radio Spectrometer at Huairou (SBRS/Huairou) during 1997-2011. The relationships between the microwave bursts and solar flares and the calibration of spectrometers are also studied.
Helicity transport from solar convection zone to interplanetary space
Authors: Zhang Mei
Published: July 2013

Magnetic helicity is a physical quantity that describes field topology. It is also a conserved quantity as Berger in 1984 demonstrated that the total magnetic helicity is still conserved in the corona even when there is a fast magnetic reconnection. It is generally believed that solar magnetic fields, together with their helicity, are created in the convection zone by various dynamo processes. These fields and helicity are transported into the corona through solar photosphere and finally released into the interplanetary space via various processes such as coronal mass ejections (CMEs) and solar winds. Here I will give a brief review on our recent works, first on helicity observations on the photosphere and how to understand these observations via dynamo models. Mostly, I will talk about what are the possible consequences of magnetic helicity accumulation in the corona, namely, the formation of magnetic flux ropes, CMEs taking place as an unavoidable product of coronal evolution, and flux emergences as a trigger of CMEs. Finally, I will address on in what a form magnetic field in the interplanetary space would accommodate a large amount of magnetic helicity that solar dynamo processes have been continuously producing.
Magnetic helicity ejections and coronal activity
Authors: Nindos A.
Published: July 2013

Magnetic helicity quantifies the degree of linkage and/or twistedness in the magnetic field. It is probably the only physical quantity which is approximately conserved even in resistive MHD. This makes it an ideal tool for the exploration of the physics of solar eruptions. In this article, I discuss the sources of magnetic helicity injected into active regions and I point out that coronal mass ejections (CMEs) are probably necessary to remove at least part of the excess helicity produced in the Sun. I also discuss the importance of magnetic helicity in the overall coronal evolution that may lead to eruptions.
Magnetic helicity injection in NOAA 11261 associated with flares
Authors: Xu Haiqing , Zhang Hongqi , Su Jiangtao , Ruan Guiping , liu Jihong
Published: July 2013

Magnetic helicity was found important in understanding solar activities such as flares and coronal mass ejections (CME). Berger and field (1984) derived an expression for helicity flux dHm/dt, that can be applied to an individual solar active region (AR) occupying an area S of the photosphere,
(1)
\begin{linenomath}
dH_{m}/dt=-2\int_{s}[(\mathbf{A_{p}}\cdot \mathbf{V})\mathbf{B}-(\mathbf{A_{p}} \cdot \mathbf{B})\mathbf{V}] dS, \eqno{(1)}
\end{linenomath}

where Ap is the vector potential of potential field, and V is the plasma velocity at the surface S. The first term describes the effect of magnetic footpoint motions on the surface S. The second term describes the flux of helicity advected through the surface when already twisted and/or writhed flux ropes emerge. Chae (2001) proposed a method of self-consistently determining magnetic helicity injection rate, dH/dt, using a time series of longitudinal magnetograms only:
(2)
\begin{linenomath}
dH/dt=-\int2(\textbf{A}_{p}\cdot \textbf{V}_{LCT})B_{n}dS, \eqno{(2)}
\end{linenomath}

where n is the normal component of magnetic field. Ap is the vector potential computed from Bn by Fourier transform method. VLCT is the horizontal component of velocity determined by the technique of local correlation tracking (LCT). This technique was applied by some scientists (e.g., Chae et al., 2001; Nindos and Zhang, 2002; Romano et al., 2003). Magnetic helicity injection was found to be strongly correlated with the occurrence of major flares (Moon et al. 2002a, 2002b; Park et al., 2008; Labonte et al., 2007; Maeshiro et al., 2009).