bluuebunny/crossref_metadata_2025 huggingface dataset:
Turkish Entrepreneurship in Europe
Authors: Baycan Tüzýn
Published: July 2013

Turkish migrants constitute the largest migrant community as well as the largest migrant entrepreneurial group in many European countries. Recent studies state that today 1 in 10 Turkish families is self-employed and the number of Turkish entrepreneurs operating all over EU member states has exceeded 100,000. Projections suggest that 190,000 Turkish entrepreneurs will be living in the EU member states in 2020 while employing over 1 million people. An increasing involvement of second-generation migrants in entrepreneurial activities, as well as the new orientations from traditional to non-traditional sectors and transnational activities, has led to a transformation from ‘Migrant Entrepreneurship’ towards the ‘New European Entrepreneurship’.
Turkey and Europe: Locating Homeland Ties and Re-scaling Migration Scholarship
Authors: Caglar Ayse
Published: July 2013

This article aims to open a theoretical space to address the variation of migrant settlement and transnationalism in time and space beyond the national scale and ethnic lens. On the basis of the emergent homeland ties and Hometown Associations of Syriac migrants from Mardin (Turkey) in Europe it approaches migrant dynamics through the lens of the repositioning struggles Mardin has undergone within the context of neo-liberal development agendas.
Core–Periphery Relations in the European Union and the Role of Central Places in Europe with a Focus on Regional Policy in Britain and Germany
Authors: Thomas Bennett C.
Published: July 2013

Core–periphery analysis is vital to an understanding of the European Union (EU) and regional development. The European Economic Community (EEC), which would eventually become the EU, was formed in 1957 in order to promote progressive economic integration. Recognizing that there were depressed regions within both peripheral and core nation-states, the EC adopted a programme with the goal of bringing those regions into convergence. Its programme is essentially a liberal centre–periphery model similar to the one proposed by Friedman. Many of the nation-states within the EC also have their own regional policies and programmes regarding intervention within their own spatial boundaries. To present an approach for comparison this article will focus on two examples of regional policy: Britain's attitude toward regional development in the North and the German programme for integrating East Germany.
Correlates of adiposity in a Caribbean pre-school population
Authors: Ramcharitar-Bourne Anisa , Nichols Selby , Badrie Neela
Published: July 2013

Objective

To evaluate ethnic and anthropometric correlates of adiposity among a nationally representative, multi-ethnic, Trinidadian pre-school population.

Design

Cross-sectional study conducted between June 2008 and July 2009.

Setting

Government and privately owned Early Childhood Care and Education Centres in Trinidad.

Subjects

A total of 596 pre-school children (aged 31–73 months) from thirty-four schools had their weight, height, mid-upper arm circumference, waist circumference, biceps and triceps skinfold thicknesses measured by a registered dietitian using standard procedures. Percentage body fat was estimated using a foot-to-foot bioelectric impedance analyser (Tanita 531, Tokyo, Japan). Date of birth, religion and ethnicity were extracted from school records and pre-schoolers’ ethnicity was categorized as East Indian, African, Mixed (a combination of two or more ethnicities), Chinese or Caucasian.

Results

Anthropometric variables explained significantly more of the variance in adiposity among girls (67·4–88·1 %) than boys (24·4–39·2 %;P< 0·0 0 1). Pre-schoolers of African descent were significantly taller, heavier and had higher abdominal fat and mid-upper arm circumference than their East Indian and Mixed counterparts (allP< 0·001). The overall prevalence of excess adiposity (≥25 % body fat) as determined by bioelectrical impedance was 14·6 %, while 2·9 % of the children were undernourished according to WHO weight-for-age criteria. Differences in anthropometry were non-existent between children attending government and private pre-schools.

Conclusions

Gender, ethnicity and anthropometry all explained excess adiposity in these pre-schoolers. These findings highlight the need to elucidate the mechanisms that may be involved in explaining these differences, particularly those of ethnic origin.
A DUAL-RECIPROCITY BOUNDARY ELEMENT METHOD FOR STEADY INFILTRATION PROBLEMS
Authors: SOLEKHUDIN I. , ANG K. C.
Published: July 2013

Steady water infiltration in homogeneous soils is governed by the Richards equation. This equation can be studied more conveniently by transforming to a type of Helmholtz equation. In this study, a dual-reciprocity boundary element method (DRBEM) is employed to solve the Helmholtz equation numerically. Using the solutions obtained, numerical values of the suction potential are then computed. The proposed method is tested on problems involving infiltration from different types of periodic channels in a homogeneous soil. Moreover, the method is also examined using infiltration from periodic trapezoidal channels in three different types of homogeneous soil.
PROFINITE GROUPS WITH FINITE VIRTUAL LENGTH
Authors: GAVIOLI NORBERTO , MONTI VALERIO , SCOPPOLA CARLO MARIA
Published: July 2013

In this paper we introduce the notion of finite virtual length for profinite groups (that is, every series has a bounded number of infinite factors) and we prove a Jordan–Hölder type theorem for profinite groups with finite virtual length. More structural results are provided in the pronilpotent and$p$-adic analytic cases.
ON CLEAN LAURENT SERIES RINGS
Authors: ZHOU YIQIANG , ZIEMBOWSKI MICHAŁ
Published: July 2013

Here we prove that, for a $2$-primal ring $R$, the Laurent series ring $R((x))$ is a clean ring if and only if $R$ is a semiregular ring with $J(R)$ nil. This disproves the claim in K. I. Sonin [‘Semiprime and semiperfect rings of Laurent series’, Math. Notes 60 (1996), 222–226] that the Laurent series ring over a clean ring is again clean. As an application of the result, it is shown that, for a $2$-primal ring $R$, $R((x))$ is semiperfect if and only if $R((x))$ is semiregular if and only if $R$ is semiperfect with $J(R)$ nil.
Treatment planning comparison between high dose rate and intensity-modulated radiation therapy for prostate cancer as a means of boost dose
Authors: Bose Satya , Bahri Sanjeev , Lalonde Ron
Published: July 2013

Purpose

The main objective of this study was to compare dosimetric characterisation of high-dose-rate brachytherapy (HDR-BT) with external beam intensity-modulated radiation therapy (EX-IMRT) as a means of delivering boost dose.

Materials and methods

Five HDR patients were selected for IMRT planning. Patients underwent ultrasound-guided catheter placement for HDR. Computed tomography (CT) images were obtained and imported into the Nucletron PLATO Brachytherapy system. The prostate, urethra, bladder and rectum were contoured on axial slices. The dose was calculated and optimised by graphical optimisation. The CT images of these structures were exported from the PLATO to Eclipse workstation for IMRT planning. For each patient, the dose–volume histogram (DVH) of HDR and IMRT plans were generated, drawn on the same scale and compared.

Results

The dose distribution in HDR plans was non-uniform and conformed peripherally inside the planned target volume (PTV). A small volume of the prostate received a very high dose from HDR.In IMRT plans, a uniform dose distribution was observed. The DVH curves for PTV dropped sharply and reached to a zero volume of the prostate at about 6·4 Gy. In HDR plans, the DVH curves for PTV showed a long tail up to a very high dose. About 10% of the prostate received about 13·3 Gy, which is 222% of the prescribed dose (6 Gy) in HDR plans. In contrast, the same volume in IMRT plans received <6 Gy (100%). The average dose for V90 was about 6·3 Gy for HDR and 5·8 Gy for IMRT plans. At a prostate volume of V100 level, the average dose in all plans was 5·0 Gy from HDR and 5·4 Gy from IMRT plans. In HDR plan, the V100 dose for urethra varied from 0·6 to 3·0 Gy (average 1·8 Gy). The range in IMRT plans varied from 3·6 to 6 Gy with an average of 4·7 Gy. At V90 level, the dose range in HDR and IMRT plans varied from 2·5 to 4·7 Gy (average 3·8 Gy) and 4·8 to 5·4 Gy (average 5·3 Gy), respectively. In general, the dose to the bladder and rectum was comparatively lower in HDR than in IMRT plans.

Conclusions

HDR brachytherapy may reduce normal tissue toxicities in prostate boost treatments, even though the dose homogeneity inside the PTV is far worse than in IMRT treatments. Another advantage of HDR over IMRT is that the organ motion is not a significant concern as in IMRT.
Variation for selected morphological and quality-related traits among 178 faba bean landraces collected from Turkey
Authors: Karaköy Tolga , Baloch Faheem Shehzad , Toklu Faruk , Özkan Hakan
Published: July 2013

Faba bean is cultivated worldwide and widely used in Mediterranean countries, Asia and Europe. However, only a few faba bean breeders are active in cultivar development. As a result, a limited number of varieties are available for growers. Plant genetic resources or germplasm are fundamental sources for plant breeding, and the assessment of the genetic diversity among germplasm accessions is useful to facilitate more efficient use of plant genetic resources. A mini-core collection of faba bean germplasm (178 landraces and four cultivars), from diverse geographic regions of Turkey, was assessed for agro-morphological performance and some quality traits. There were substantial variations for the investigated morphological and quality characteristics. The analysis of variance revealed that the differences among 182 accessions were significant for all the studied characters. Some accessions showed very good agronomic performance for some traits. Positive and negative correlations existed among different morphological and agronomic traits. Landraces have been classified into four different groups using a cluster analysis. These results suggest that an a priori classification of accessions according to the growing area does not strictly correspond to phenotypic grouping. From the spatial distribution of landraces, however, it has been possible to identify ‘superior’ accessions of some traits. These findings indicate a number of useful traits in the gene pools and a wide range of phenotypic variation that provides a good source of diversity for use in modern faba bean breeding programmes.
Plant and fruit trait variations among four Capsicum species in a Caribbean germplasm collection
Authors: Bharath Sarah M. , Cilas Christian , Umaharan Pathmanathan
Published: July 2013

Despite Capsicum's importance in the Caribbean, comprehensive diversity studies of this species in the region are limited, especially regarding its morphological variation. This study evaluated 37 traits (seedling, vegetative and reproductive) in 201 accessions among four Capsicum species. Multivariate analyses revealed that (i) 54% of the quantitative (seedling and fruit) variation and (ii) 64% of the qualitative (floral and fruit) variation were explained by the first two components. The three main clusters identified did not immediately highlight geographic and species-specific separation. However, significance testing revealed some separation based on geographic subgroups and species assignment. Most Southern Caribbean accessions were considerably similar to each other (if not identical in some cases), thus providing opportunity to identify and remove duplicates from the collection. These Southern Caribbean accessions shared their greatest similarity with Upper Amazon accessions, and least similarity with Lower Amazon accessions, suggesting movement of material primarily from the Upper Amazon into the Southern Caribbean Basin. The dominant differentiating traits displayed in these Southern Caribbean accessions are probably due to strong active selection for certain morphotypes and not to founder effects. Upper and Lower Amazon accessions were largely well differentiated from each other, highlighting key underlying genetic differences between these two populations and possible ongoing barriers to germplasm exchange. Central American, Greater Antilles/Bahamas and Guiana Shield accessions shared similarities with both the Upper and Lower Amazon populations, hinting at probable introductions from both Amazon regions. Collectively, this provides essential baseline information on the morphological (and underlying genetic) relationships among these accessions to guide future characterisation and evaluation efforts on this collection.
Helioseismic measurements of differential rotation and meridional flow
Authors: Zhao Junwei
Published: July 2013

Solar interior differential rotation and meridional flow play important roles in dynamo models. In this review, I briefly review results in interior rotational profiles and zonal flows obtained from helioseismology studies. Due to the new developments in recent years in interior meridional flow studies, this review focuses more on results on meridional flow. I describe new developments in the shallower poleward meridional flow, and the temporal evolution of these flows. Then I introduce a newly identified center-to-limb variation effect in helioseismology studies, and present recent results in the search of equatorward meridional flows. I also discuss how these results will effect the dynamo models.
Observations of magnetic and kinetic helicity proxies
Authors: Zhang Hongqi
Published: July 2013

The helicity is important to present the basic topological configuration of magnetic field in solar atmosphere. The distribution of magnetic helicity in solar atmosphere is presented by means of the observational (vector) magnetograms. As the kinetic helicity in the solar subatmosphere can be inferred from the velocity field based on the technique of the helioseismology and used to compare with the magnetic helicity in the solar atmosphere, the observational helicities provide the important chance for the confirmation on the generation of magnetic fields in the subatmosphere and solar dynamo models also. In this paper, we present the observational magnetic and kinetic helicity in solar active regions and corresponding questions, except the relationship with solar eruptive phenomena.
How much more can sunspots tell us about the solar dynamo?
Authors: Norton Aimee A. , Jones Eric H. , Liu Y. , Hayashi K. , Hoeksema J. T. , Schou Jesper
Published: July 2013

Sunspot observations inspired solar dynamo theory and continue to do so. Simply counting them established the sunspot cycle and its period. Latitudinal distributions introduced the tough constraint that the source of sunspots moves equator-ward as the cycle progresses. Observations of Hale's polarity law mandated hemispheric asymmetry. How much more can sunspots tell us about the solar dynamo? We draw attention to a few outstanding questions raised by inherent sunspot properties. Namely, how to explain sunspot rotation rates, the incoherence of follower spots, the longitudinal spacing of sunspot groups, and brightness trends within a given sunspot cycle. After reviewing the first several topics, we then present new results on the brightness of sunspots in Cycle 24 as observed with the Helioseismic Magnetic Imager (HMI). We compare these results to the sunspot brightness observed in Cycle 23 with the Michelson Doppler Imager (MDI). Next, we compare the minimum intensities of five sunspots simultaneously observed by the Hinode Solar Optical Telescope Spectropolarimeter (SOT-SP) and HMI to verify that the minimum brightness of sunspot umbrae correlates well to the maximum field strength. We then examine 90 and 52 sunspots in the north and south hemisphere, respectively, from 2010 - 2012. Finally, we conclude that the average maximum field strengths of umbra 40 Carrington Rotations into Cycle 24 are 2690 Gauss, virtually indistinguishable from the 2660 Gauss value observed at a similar time in Cycle 23 with MDI.
Phase relationship between polar faculae and sunspot numbers
Authors: Deng L. H.
Published: July 2013

Linear and nonlinear approaches are used to investigate the phase asynchrony between the polar faculae (PF) and sunspot numbers (SNs). It is found that, (1) PF show leads of 52 months relative to SNs on the average of the considered time interval; (2) the cross-wavelet transform analysis shows that they are asynchronous in both the low- and high-frequency components. These indicate that their phase relationship is not only time-dependent but also frequency-dependent.
Comparison of solar activity during last two minima on turn of Activity Cycles 22/23 and 23/24
Authors: Gryciuk Magdalena , Gburek Szymon , Siarkowski Marek , Podgorski Piotr , Sylwester Janusz , Farnik Frantisek
Published: July 2013

The subject of our work is the review and comparison of solar activity during the last two solar minima that occurred between recent activity cycles. We use the soft X-ray global solar corona observations covering the two nine-months long time intervals in 1997/98 and 2009. Data from RF15-I multichannel photometer are used for the penultimate minimum. For the last unusually deep and prolonged solar activity minimum in 2009 the data from SphinX spectrophotometer are used. Comparison of measurements from both minima takes place in the overlapping energy range 2–15 keV. We focus on the active region formation, evolution and flaring productivity during respective minima.
Modeling the solar cycles 12-20 with a Babcock-Leighton flux transport dynamo
Authors: Jiang Jie
Published: July 2013

We use a Babcock-Leighton-type of dynamo with the poloidal source based as closely as possible on the observations to model the solar cycle irregularities during the cycles 12-20. The nonlinearities in the poloidal field generation, i.e., the cycle dependence of the sunspot group tilt angles and the latitudes are included. The convective pumping dominates the transport of the surface poloidal field to the tachocline. Our results show that the modeled polar fields have a good correlation with the observed next cycle strength and the build-up of the toroidal flux at the tachocline is strongly correlated with the observed cycle strength as well. Both correlation coefficients are above 0.8. The success of the model indicates that they are the nonlinearities in the poloidal field generation which cause the solar cycle irregularities.
On the extended 23rd solar cycle
Authors: Krivodubskij Valery N.
Published: July 2013

An explanation of the mystery of the extended 23rd solar cycle duration about 13 years in the frame of non-linear regime of the αΩ- dynamo model is proposed. The calculated dynamo-period of the solar cycle, T, depends (in the inverse proportion) on the intensity of the α- effect in the solar convection zone (SCZ). As well, the intensity of the α- effect in non-linear regime depends (also in the inverse proportion) on the value of toroidal magnetic field, BT (magnetic alpha-quenching). Thus, the calculated period is in direct proportion to the value of toroidal magnetic field: the stronger toroidal field BT in certain cycle, the longer dynamo-period T of this cycle. Since the toroidal field is hidden in the deep layers of the SCZ, it is necessary to know some other magnetic experimental evidence that reflects something like information about inner toroidal field. In this connection we allow for that the strong toroidal field is transported by magnetic buoyancy to the solar surface and produces here the sunspots, so they carry indirect information on BT. In this connection we took into account up-to-date observed data on the essential increase of the averaged annual module of the magnetic field of the large-scale sunspots, Bsp, in the 23rd cycle; and then we made calculation of the alpha-quenching which depends on these referred data. It is important to know only relative variations of magnetic index Bsp for calculation of the dynamo-period variation. Our estimations showed that the average solar period, which is about 11 years, must increase by a factor of 1,2; so the calculated 23rd cycle dynamo-period would be about 13 years.
Model of poleward magnetic field streams from sunspot butterflies
Authors: Zolotova Nadezhda V. , Ponyavin Dmitri I.
Published: July 2013

The poleward magnetic field streams on time-latitude diagram of the photospheric magnetic field of the Sun during 1975–2011 (Kitt Peak NSO, SOLIS NSO, SOHO MDI data) are modeled. We performed simulations in terms of probability density function and bipole orientation according to Joy's law and Hale's cycle. The difference between distributions of leading and trailing fluxes of bipolar sunspots defines the so-called surplus. Finally, magnetic field streams and polar field reversals are a result of meridional drift of a surplus to the poles.
Spectropolarimetric diagnostics of unresolved magnetic fields in the quiet solar photosphere
Authors: Shchukina Nataliya G. , Bueno Javier Trujillo
Published: July 2013

A few years before the Hinode space telescope was launched, an investigation based on the Hanle effect in atomic and molecular lines indicated that the bulk of the quiet solar photosphere is significantly magnetized, due to the ubiquitous presence of an unresolved magnetic field with an average strength 〈B〉, ≈ 130 G. It was pointed out also that this “hidden” field must be much stronger in the intergranular regions of solar surface convection than in the granular regions, and it was suggested that this unresolved magnetic field could perhaps provide the clue for understanding how the outer solar atmosphere is energized. In fact, the ensuing magnetic energy density is so significant that the energy flux estimated using the typical value of 1 km/s for the convective velocity (thinking in rising magnetic loops) or the Alfvén speed (thinking in Alfvén waves generated by magnetic reconnection) turns out to be substantially larger than that required to balance the chromospheric energy losses. Here we present a brief review of the research that led to such conclusions, with emphasis on a new three-dimensional radiative transfer investigation aimed at determining the magnetization of the quiet Sun photosphere from the Hanle effect in the Sr I 4607 Å line and the Zeeman effect in Fe I lines.
Nature of the solar dynamo at small scales
Authors: Stenflo J. O.
Published: July 2013

It is often claimed that there is not only one, but two different types of solar dynamos: the one that is responsible for the appearance of sunspots and the 11-yr cycle, frequently referred to as the “global dynamo”, and a statistically time-invariant dynamo, generally referred to as the “local dynamo”, which is supposed to be responsible for the ubiquitous magnetic structuring observed at small scales. Here we examine the relative contributions of these two qualitatively different dynamos to the small-scale magnetic flux, with the following conclusion: The local dynamo does not play a significant role at any of the spatially resolved scales, nearly all the small-scale flux, including the flux revealed by Hinode, is supplied by the global dynamo. This conclusion is reached by careful determination of the Sun's noise-corrected basal magnetic flux density while making use of a flux cancellation function determined from Hinode data. The only allowed range where there may be substantial or even dominating contributions from a local dynamo seems to be the scales below about 10 km, as suggested by observations of the Hanle depolarization effect in atomic spectral lines. To determine the fraction of the Hanle depolarization that may be due to the action of a local dynamo, a synoptic program is being initiated at IRSOL (Istituto Ricerche Solari Locarno).
Origin of quiet-Sun magnetic fields revealed with Hinode
Authors: Ishikawa Ryohko
Published: July 2013

Quiet-Sun magnetic fields are enigmatic in terms of their properties, and their origin is not well understood. One likely possibility is that they are a consequence of interactions with turbulent convective motions of various temporal and spatial scales. Here we investigate the relationship between small-scale magnetic fields and various convection flows. We demonstrate that in addition to granulation and supergranulation, mesogranulation also plays an important role in structuring quiet-Sun magnetic fields. We also study the vector magnetic fields in the quiet Sun, and propose that emerging granular-scale bipolar loops are major sources of the quiet-Sun magnetic fields.
Self-cancellation of solar ephemeral regions observed by SDO
Authors: Yang Shuhong , Zhang Jun , Li Ting , Liu Yang
Published: July 2013

We study the ephemeral regions (ERs) in the quiet Sun observed by the Solar Dynamics Observatory, and find that they can be classified into two types: normal ERs (NERs) and self-cancelled ERs (SERs). We identify 2988 ERs among which there are 190 SERs, about 6.4% of the ERs. The total self-cancelled flux is 9.8% of the total ER flux. We suggest that the self-cancellation of SERs is caused by the submergence of magnetic loops connecting the dipolar patches, without magnetic energy release.
Magnetic field generation in an accretion disk of close binary star
Authors: Bisikalo Dmitry V. , Zhilkin Andrey G.
Published: July 2013

Using results of 3D MHD numerical simulations we investigate the generation of the magnetic field in an accretion disk of a close binary star. Analysis of the numerical simulations shows that the magnetic field, which is mainly toroidal, is intensively generated in the accretion disk. In the disk, we can distinguish three regions: inner region of the intensive toroidal field generation due to the differential rotation; region of the current sheets; and outer region of the magnetic field dissipation. In the outer regions of the accretion disk of a magnetic close binary system two types of the dynamo may exist. One of them is the laminar dynamo that occurs as a result of the nonaxisymmetric motions. The other type is the turbulent αω-dynamo. Numerical simulations show that during the disk lifetime the dynamo effect in the outer region of the disk can be significant.
On the behavior of stellar rotation in the solar neighbourhood
Authors: de Freitas Daniel B. , De Medeiros J. R.
Published: July 2013

Rotation is a fundamental physical parameter in stellar astrophysics, playing an important role on the formation and evolution of stars. This parameter may also offer valuable information on stellar magnetism, mixing in the stellar interior, tidal interactions in close binary, as well as on angular momentum transfer and rotational breaking due to planets. The present work brings the results of an unprecedented study on the behavior of the distribution of the projected rotational velocity (v sin i) as a function of galactic position, on the basis of an unique sample of 14000 main-sequence field stars, along the spectral regions F and G. The vsini measurements used in this analyses were obtained from observations carried out with the CORAVEL spectrometers, with a precision better than about 1 km/s.
Effect of magnetic fields on Lithium depletion of solar-type stars
Authors: Li Tanda , Bi Shaolan
Published: July 2013

To study the effect of magnetic fields on lithium depletion and explain the characters of lithium evolution in solar-type stars, stellar models including Tayler-Spruit dynamo-type field are constructed. We compare the theoretical results with the time scales of lithium depletion suggested by Sestito & Randich (2005) and obtain very good agreements.
Fundamental properties and seismological analysis of three Kepler stars
Authors: Liu K. , Bi S. L.
Published: July 2013

The lithium abundance of KIC 11395018 and KIC 10920273 are not compatible with their age, which is deduced by asteroseismology. To explain this phenomenon, we investigate the possible evolutionary status and perform seismological analysis of the three stars KIC 11395018, KIC 10273246 and KIC 10920273. Using the Yale Rotating Stellar Evolution Code (YREC), we constructed a grid of evolutionary tracks with different input physics and rotation rates. In addition to the conventional observed properties, we added two observed constraints: lithium abundance and rotational period. As a result, the lithium abundance of our rotation models agrees well with the observation. Meanwhile, we obtained a set of more accurate stellar fundamental parameters than previous studies.
Chromospheric activity of late-type stars based on Guoshoujing Telescope
Authors: Zhang Liyun , Shi Jianrong , Zhao Jingkun , Luo Ali , Zhang Guoyin , Pi Qingfeng ,   for the Guoshoujing Telescope Collaboration
Published: July 2013

We introduced our preliminary results of chromospheric activity of late-type stars based on the stellar spectrum of the pilot survey of the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST, also called Guo Shou Jing telescope). We have found 1151 active M stars from 17471 M samples using the chromospheric active indicator of the Hα line.
Galactic spiral patterns and dynamo action
Authors: Chamandy Luke , Subramanian Kandaswamy , Shukurov Anvar
Published: July 2013

The theory of mean-field galactic dynamos is generalized by allowing for a finite response time of the mean electromotive force (emf) to variations in the mean magnetic field and small-scale turbulence. A non-axisymmetric forcing of the dynamo by a spiral pattern (either stationary or transient) is invoked. The resulting magnetic spiral arms are phase-shifted from the spiral arms of the pattern by an angle 15°–40°, opposite to the sense of galactic rotation. Our findings may help to explain the phase shift between material and magnetic arms observed in NGC 6946 and other galaxies.
Growth rate of magnetic field during starburst phase in a galaxy
Authors: Ko Chung-Ming
Published: July 2013

During an active star formation phase, it is conceivable that the turbulent level of a galaxy increases and consequently an increase in magnetic field by turbulent dynamo process. We point out that the thickness of the dynamo region is sensitive to the turbulent level. We examine the linear growth rate of three different dynamos, namely, αω, α2ω and α2 dynamos. We find that the dependence of the growth rate on turbulent level is quite different for different dynamos. Moreover, the growth rate is not necessary monotonic to turbulence level even in the linear regime.
Astrophysical MHD turbulence: confluence of observations, simulations, and theory
Authors: Burkhart Blakesley , Lazarian Alex
Published: July 2013

Magnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.
Turbulence and dynamo interlinks
Authors: de Gouveia Dal Pino E. M. , Santos-Lima R. , Kowal G. , Falceta-Gonçalves D.
Published: July 2013

The role of turbulence in astrophysical environments and its interplay with magnetic fields is still highly debated. In this lecture, we will discuss this issue in the framework of dynamo processes. We will first present a very brief summary of turbulent dynamo theories, then will focus on small scale turbulent dynamos and their particular relevance on the origin and maintenance of magnetic fields in the intra-cluster media (ICM) of galaxies. In these environments, the very low density of the flow requires a collisionless-MHD treatment. We will show the implications of this approach in the turbulent amplification of the magnetic fields in these environments. To finalize, we will also briefly address the connection between MHD turbulence and fast magnetic reconnection and its possible implications in the diffusion of magnetic flux in the dynamo process.
Saturation of the magnetorotational instability by stable magnetoacoustic modes
Authors: Liverts Edward , Shtemler Yuri , Mond Michael , Umurhan Orkan M. , Bisikalo Dmitry V.
Published: July 2013

The magnetorotational instability (MRI) of thin, vertically-isothermal Keplerian discs, under the influence of an axial magnetic field is investigated near the instability threshold. The nonlinear interaction of Alfven-Coriolis (MRI) modes with stable magnetoacoustic waves is considered. The transition of the Alfven-Coriolis modes to instability occurs when the linearized system has zero eigenvalue of multiplicity two. As a result the nonlinear ordinary differential equation that describes the evolution of the amplitude of the MRI mode near the threshold is of second order. Solutions of that amplitude equation reveal that the MRI is saturated to bursty periodical oscillations due to the transfer of energy to the stable magnetosonic modes.
Modelling grand minima of solar activity using a flux transport dynamo model
Authors: Karak Bidya Binay , Choudhuri Arnab Rai
Published: July 2013

The occurrence of grand minima like the Maunder minimum is an intriguing aspect of the sunspot cycle. We use the flux transport dynamo model to explain the grand minima, showing that they arise when either the poloidal field or the meridional circulation falls to a sufficiently low value due to fluctuations. Assuming these fluctuations to be Gaussian and determining the various parameters from the data of the last 28 cycles, we carry on a dynamo simulation with both these fluctuations. The results are remarkably close to the observational data.
Observational methods for stellar magnetism: from detection to cartography
Authors: Strassmeier Klaus G. , Carroll Thorsten A. , Ilyin Ilya , Järvinen Silva
Published: July 2013

We review some of the currently used techniques to detect stellar magnetic fields on cool stars. Emphasis is put on spectropolarimetry with high-resolution spectrographs and its related data de-noising techniques and multi-line inverse modeling. Detections and results from Zeeman splittings and broadenings are briefly mentioned. We discuss some of our most recent Zeeman Doppler Imaging (ZDI) results and present a comparison of ZDI maps of the K-type WTTS V410 Tauri and the planet-hosting F8 star HD 179949 with results from other groups.
Prospect on intergalactic magnetic field measurements with gamma-ray instruments
Authors: Sol Hélène , Zech Andreas , Boisson Catherine , Krawczynski Henric , Fallon Lisa , de Gouveia Dal Pino Elisabete , Hinton Jim , Inoue Susumu , Neronov Andrii , White Richard
Published: July 2013

Observing high-energy gamma-rays from Active Galactic Nuclei (AGN) offers a unique potential to probe extremely tiny values of the intergalactic magnetic field (IGMF), a long standing question of astrophysics, astroparticle physics and cosmology. Very high energy (VHE) photons from blazars propagating along the line of sight interact with the extragalactic background light (EBL) and produce e+e− pairs. Through inverse-Compton interaction, mainly on the cosmic microwave background (CMB), these pairs generate secondary GeV-TeV components accompanying the primary VHE signal. Such secondary components would be detected in the gamma-ray range as delayed “pair echos” for very weak IGMF (B < 10−16G), while they should result in a spatially extended gamma-ray emission around the source for higher IGMF values (B > 10−16G). Coordinated observations with space (i.e. Fermi) and ground-based gamma-ray instruments, such as the present Cherenkov experiments H.E.S.S., MAGIC and VERITAS, the future Cherenkov Telescope Array (CTA) Observatory, and the wide-field detectors such as HAWC and LHAASO, should allow to analyze and finally detect such echos, extended emission or pair halos, and to further characterize the IGMF.
How the planetary research helps to the stellar dynamo understanding
Authors: Boisse I. , Oshagh M. , Lovis C. , Santos N. C. , Dumusque X. , Bonfils X. , Montalto M. , Boué G.
Published: July 2013

Most of the exoplanet science is dependent on the stellar knowledge. One of them that has to be understood is the magnetic activity when we search for planets with radial velocity or photometry measurements. The main shape of stellar activity and spots properties have to be understood, for example, to choose the best targets to search for low-mass planets in the habitable zone or to derive the accurate parameters of a planetary system. With that aim, we show in this presentation how these studies lead to give clues on spots latitudes and on the long term variation of stellar activity. The properties of magnetic activity on the low rotators solar-type stars are not easily reachable by other techniques (spectropolarimetry or Doppler imaging) and these studies should be used to constrain theories of stellar dynamo.
Solar initiative at Oukaimeden Observatory
Authors: Benkaldoun Zouhair , Makela Jonathan J. , Meriwether John W.
Published: July 2013

The solar research program at Oukaimeden Observatory started in 1988 with the helioseimological IRIS network. The Moroccan researchers involved in this research have analyzed solar observations in order to detect and characterize the solar sphere modes of oscillations. In the coming year, the researchers at the Oukaimeden Observatory will add new research capabilities by joining the International Space Weather Initiative (ISWI), installing a suite of optical instruments, comprising a Remote Equatorial Nighttime Observatory of Ionospheric Regions (RENOIR). The scope and objectives to be achieved in this proposed project are to:

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deploy a Fabry-Perot interferometer and wide-angle imaging system to the Observatoire Astronomique Universitaire de LOukaimeden;

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train students and researchers from Cadi Ayyad University on the operation of the equipment and related analysis techniques;

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collect and analyze data from the equipment to study properties of upper-atmospheric winds and temperatures and how they relate to the occurrence of space weather; and

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develop an international collaboration network with other researchers using similar instrumentation in Brazil and Peru. We will present here the plan we intend to develop for the Moroccan solar program in connection with ISWI.
Observations of interplanetary scintillation in China
Authors: Liu Li-Jia , Peng Bo
Published: July 2013

The Sun affects the Earth in multiple ways. In particular, the material in interplanetary space comes from coronal expansion in the form of solar wind, which is the primary source of the interplanetary medium. Ground-based Interplanetary Scintillation (IPS) observations are an important and effective method for measuring solar wind speed and the structures of small diameter radio sources. In this paper we will discuss the IPS observations in China.
An intelligent method for solar flare observation
Authors: Lin Jia Ben , Guo Juan , Deng Yuan Yong
Published: July 2013

To capture the fine structure of the flare kernel during it's explosive phase, we design a real time flare onset detecting algorithm named Near Saturation Area Threshold(NSAT), And an automatic CCD parameters control algorithm for the observing software. All the data from CCD, 48f/s, could be saved to the hard disk, and the GPS time of the flare onset also be saved in the log. These methods could avoid the data overflow and grab the fine structure data of the flare kernel. The simulation experiment works well and the software will be put into use in Huairou Solar Observatory soon.
Connections beween photospheric current helicity, flares and solar subsurface kinetic helicity
Authors: Gao Yu , Zhao Junwei , Zhang Hongqi
Published: July 2013

The α-effect is central to magnetic field generation in αΩ dynamo theory (Parker, 1955), however, it lacked observational and experimental supports over a long term (Sokoloff, 2007). Mirror asymmetries of magnetic field (magnetic helicity) were not observed until the recent 20 years (Seehafer, 1990; Pevtsov et al., 1995, Bao & Zhang, 1998). Later, the advancement in local helioseismology has made possible the measurements of solar subsurface velocity field and the vorticity (or kinetic helicity) as well (Zhao & Kosovichev, 2003). Apparently, frozen flow with the magnetic field in the fluid of high magnetic Reynold number is a necessary condition for the α-effect in the framework of Parker's dynamo model.
Space environment during Solar Minimum of SC-23
Authors: Hady Ahmed A.
Published: July 2013

Geomagnetic and solar storms and their occurrence rate with respect to the solar activity cycle is an important topic of space environment research. The minimum of solar activity during the solar cycle number 23 (SC-23) have detectable effects on the space environments, where the monthly mean of sunspot number and solar proton events effecting the space environment and produced many of Geophysical effects. A detailed study of the centers of activity produced the proton events are carried out. The electromagnetic emissions at the different bands during the impulsive phase of the flare are tabulated and discussed. The different Geophysical effects due to the events are studied. Conclusions about the proton solar events at minimum activity are presented.
The helicity, induced electric field and Poynting flux of AR 11158
and their relationship with the X-class flare
Authors: Liu Jihong , Su Jiangtao , Zhang Hongqi
Published: July 2013

With the photospheric vector magnetic fields provided by SDO/HMI team, the helicity accumulation, induced electric field and Poynting flux is calculated for AR 11158 by using the local correlation tracking technique (LCT). It is found that the helicity accumulation reaches 6000×1040Mx2, the average densities of the induced electric field about 0.15-0.35 V cm−1, and that of the Poynting flux about 50-240 W m−2, within 50 hours. One main flare of X2.2 occurs in the increasing phase of the helicity accumulation, which also corresponds to the decreasing phase of the induced electric field and the gradual change phase of the Poynting flux. Before the flare, all these quantities increase rapidly for about 20 hours firstly, then increase gradually or even decrease for 8-9 hours.
Probing the solar origin of energy build-up and release in solar energetic particles
Authors: Awasthi Arun Kumar , Jain Rajmal , Bhatt Nipa J.
Published: July 2013

We study the temporal and spatial evolution of magnetic field parameters, and multi-wavelength observations of the AR 11226 and AR 11261, observed during 02-09 June 2011 and 31 July to 06 August 2011 respectively, to probe the origin of the associated solar energetic particles (SEPs). The magnetic-field toplogy of both ARs shows complex magnetic structure of β and βγ configuration. The X-ray observations by GOES and RHESSI reveal that the AR 11226 as well as AR 11261 has been most turbulent to produce flares accompanying CMEs and SEPs. We restrict our study of magnetic field evolution of ARs to helio-longitudes E20-W70. The AR 11226 produced 28 flares (⩾ GOES C-class) and 8 CMEs as well as 5 SEPs. On the other hand, the AR 11261 produced 29 flares (⩾ GOES C class), 8 CMEs as well as 5 SEPs. We study the temporal evolution of magnetic field parameters viz. gradient, shear, rotation to probe the origin of the energy release in the flare and associated CME and SEP. We do not find convincing relationship in view of predicting SEPs.
Coordinate flares observed by TRACE
Authors: Kong Defang , Yan Xiaoli , Xue Zhike
Published: July 2013

Two flares occurred simultaneously in active region NOAA 9433 on 2001 April 25. The GOES X-ray fluxes show only one peak during the two flares. The negative magnetic polarities in the two flaring regions exhibited a clockwise rotation motion around the positive polarities, which can be seen from the evolution of the SOHO/MDI magnetograms. Through analyzing the potential fields extrapolated from the MDI magnetogram, we find that there is a channel strode by a group of magnetic field lines connecting the two flaring regions.
Polar jet kinetics and energetics analysed from STEREO/COR data
Authors: Feng Li , Gan Weiqun
Published: July 2013

We analyze coronagraph observations of a polar jet eruption observed by SECCHI/STEREO. The brightness distribution of the jet in white-light coronagraph images is compared with a kinetic particle model. In this first application, we consider only gravity as the dominant force on the jet particles along the magnetic field. The kinetic model explains well the observed brightness evolution. The initial particle velocity distribution is fitted by Maxwellian distributions and we find deviations of the high energy tail from the Maxwellian distributions. The jets total mass is between 3.2×1014 and 1.8×1015 g. The total kinetic energy of all the particles in the jet source region amounts from 2.1×1028 to 2.4×1029 ergs.
Peculiar microwave quasi-periodic pulsations with zigzag pattern in a CME-related Flare on 2005-01-15
Authors: Tan Baolin
Published: July 2013

A microwave quasi-periodic pulsation with zigzag pattern (Z-QPP) in a solar flare on 2005-01-15 is observed by the Chinese Solar Broadband Spectrometer in Huairou (SBRS/Huairou) at 1.10-1.34 GHz. The zigzag pulsation occurred just in the early rising phase of the flare with weakly right-handed circular polarization. Its period is only several decades millisecond. Particularly, before and after the pulsation, there are many spectral fine structures, such as zebra patterns, fibers, and millisecond spikes. The microwave Z-QPP can provide some kinematic information of the source region in the early rising phase of the flare, and the source width changes from ~1000 km to 3300 km, even if we have no imaging observations. The abundant spectral fine structures possibly reflect the dynamic features of non-thermal particles.
A statistical study on photospheric active-region magnetic nonpotentiality and associated flares during solar cycles 22 – 23
Authors: Yang Xiao , Zhang HongQi , Lin GangHua , Gao Yu , Guo Juan
Published: July 2013

Using photospheric data obtained by vector magnetograph in Huairou Solar Observing Station of China, we have statistically studied the strength evolution of several magnetic nonpotentiality measures, along with a quantified parameter characterizing the active-region magnetic complexity – effective distance, and their relationship with associated flares during the latest 22nd and 23rd solar cycles. And the flare-prediction performance of these magnetic nonpotentiality and complexity parameters is verified by a machine learning technique.
Relaxation of magnetic field relative to plasma density during solar flares
Authors: Yu Sijie , Yan Yihua , Tan Baolin
Published: July 2013

We investigated the variations of 74 microwave ZP structures observed by Chinese Solar Broadband Radio Spectrometer at 2.6–3.8 GHz in 9 solar flares, found that the ratio between the plasma density scale height LN and the magnetic field scale height LB in emission source displays a tendency of decrease during the flaring process, indicates that LB increases faster than the LN during solar flares. The detailed analysis of the step-wise decrease of LN/LB in three typical X-class flares reveals the magnetic field relaxation relative to the plasma density.