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12/04/2013, 10:00
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12/04/2013, 10:30
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12/04/2013, 11:30
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12/04/2013, 12:00
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Dmitry Sokoloff12/04/2013, 12:30
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Mikkel Lund (Stellar Astrophysics Centre, Aarhus University)15/04/2013, 14:00
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15/04/2013, 16:00
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Prof. Kandaswamy Subramanian16/04/2013, 11:00The talk discusses the possibility that cosmic magnetic fields can originate in the early universe. Primordial fields could be generated during one of the early universe phase transitions like, inflation or the elctroweak/QCD phase transitions. We discuss these possibilities, their subsequent evolution, and the possible signals they leave on the Cosmic microwave background and on...Go to contribution page
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Leonid Kitchatinov (Institute for Solar-Terrestrial Physics)16/04/2013, 16:00
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Dr Nobumitsu Yokoi (Institute of Industrial Science, University of Tokyo)17/04/2013, 11:00Effect of cross helicity (velocity--magnetic-field correlation) in the mean momentum equation is investigated. Turbulent cross helicity enters the expression for the mean-field Lorentz force. Combined with the contributions through the Reynolds and turbulent Maxwell stresses, it gives a possibility to induce a flow. Mean momentum equation is examined from this viewpoint. As for some...Go to contribution page
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17/04/2013, 16:00
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Ana Borisova (Institute of Astronomy and NAO-Rozhen, Bulgarian Academy of Sciences)18/04/2013, 11:00
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19/04/2013, 10:30
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Johansen19/04/2013, 15:00
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Friedrich Busse22/04/2013, 11:00
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Mr Rainer Arlt (Leibniz Institute for Astrophysics Potsdam)23/04/2013, 11:00
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Levente Kriskovics (Konkoly Observatory of the Hungarian Academy of Sciences, Budapest)23/04/2013, 15:30SeminarFast rotating red giant branch stars in the first dredge-up phase provide a unique opportunity to study connections between enhanced Li abundance and activity. DI Psc is (HD 217352) a Li- rich, active single K giant, a new candidate for the rather small group of giants currently in this state. We reconstructed the surface temperature distribution by the means of Doppler Imaging on...Go to contribution page
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Matteo Cantiello (Kavli Institute for Theoretical Physics, University of California)24/04/2013, 11:00SeminarRecent observations have revealed the presence of both pulsations and magnetic fields in massive stars. As these phenomena can directly affect the mass-loss and the rotation rate, their impact on stellar evolution is potentially huge, with consequences for the final fate of massive stars. I will review some of the latest observational and theoretical developments in the field, focusing in...Go to contribution page
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Alexander F. Kholtygin (Astronomical Institute, Saint-Petersburg State University)24/04/2013, 15:30SeminarThe standard method of the magnetic field measurement, based on an analysis of the relation between the Stokes V-parameter and the first derivative of the total line profile intensity, has been modified by applying a linear integral operator L to the both sides of this relation. The wavelet transform with DOG-wavelets as the operator L is used. The advantage of the method is an effective...Go to contribution page
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Nathan J. Kleeorin (Ben-Gurion University of the Negev, Beer-Sheva)25/04/2013, 11:00We discuss a new theory of differential rotation in anisotropic density stratified inhomogeneous turbulent convection. A key point of this theory is an effect of the turbulent heat flux on the Reynolds stresses in a rotating turbulent convection. We solved a coupled system of dynamical equations which includes the equations for the Reynolds stresses, the entropy fluctuations and...Go to contribution page
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Hans-Erich Fröhlich, Mr Rainer Arlt (Leibniz Institute for Astrophysics Potsdam)25/04/2013, 15:30
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Kate Rubin26/04/2013, 10:30
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Bidya Binay Karak (Department of Physics, Indian Institute of Science, Bangalore)26/04/2013, 14:00SeminarThe irregular nature of the solar cycle makes the prediction of future cycles challenging. However, the prediction of the solar activity is important for several reasons. In the Babcock-Leighton dynamo models, the poloidal field is generated near the solar surface whereas the toroidal field is generated near the base of the convection zone. Therefore a finite time necessary...Go to contribution page
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Emmanuel Dormy29/04/2013, 11:00
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Mr Rainer Arlt (Leibniz Institute for Astrophysics Potsdam)29/04/2013, 14:30
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Nadezhda V. Zolotova (Earth's Physics Department, St.Petersburg State University)29/04/2013, 15:30SeminarUsing Greenwich catalogue of sunspots and magnetic field observations it was shown that impulses of sunspot activity during a course of solar cycle are responsible for residual magnetic flux transported by meridional circulation toward the poles. This, in turn, is related to the polarity reversal of the axisymmetric magnetic fields. Single and compound magnetic field reversals at...Go to contribution page
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Kirill Kuzanyan (IZMIRAN, Russia)30/04/2013, 11:00SeminarWe study observational proxies of magnetic helicity (and the alpha effect) in the Sun by analysis of photospheric vector magnetograms. The newest finding is determination of anisotropy of helicity near the solar surface. We can demonstrate that assumptions of local homogeneity and isotropy require serious revision in the light of these findings. Furthermore, we can show that rotation...Go to contribution page
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Lúcia D. V. Duarte (Max-Planck-Institut für Sonnensystemforschung, Lindau)30/04/2013, 11:30SeminarObservations of the gas giants show that both planets have dipolar magnetic fields: Jupiter's is very similar to the Earth's magnetic field and Saturn's is very axisymmetric. In addition, both gas giants present a very dynamical behaviour of the atmospheric flow, organized in banded structures of east-west flow. Our main goal is to approach more realistic numerical models that...Go to contribution page
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Rakesh Yadav (Max-Planck-Institut für Sonnensystemforschung, Lindau)30/04/2013, 14:00SeminarNumerical dynamo models always operate at parameters which are many orders of magnitude smaller or larger than the values expected in natural objects. However, numerical modelling has been very successful in reproducing many interesting properties of dynamos existing in nature. This qualitative agreement fuels the idea that both numerical and natural systems are in an asymptotic...Go to contribution page
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Martin Schrinner30/04/2013, 15:30
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Dr Gustavo Guerrero (NORDITA)01/05/2013, 11:00
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Raynaud Raphael01/05/2013, 11:30We will present a summary of different versions of the convective approximations of the fully compressible version of the Navier-Stokes equation, and question their numerical implementation.Go to contribution page
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Prof. Alexander Kholtygin (Astronomical Institute of Saint-Petersburg University, Russia)02/05/2013, 11:00
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Illa Rivero Losada02/05/2013, 14:30
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Sarah Jabbari (KTH Royal Institute of Technology, Stockholm)02/05/2013, 15:30SeminarIn the presence of strong density stratification, turbulence can lead to a large-scale instability of a horizontal magnetic field if its strength is in a suitable range (within a few percent of the turbulent equipartition value). This instability is related to a suppression of the turbulent pressure so that the turbulence contribution to the mean magnetic pressure becomes...Go to contribution page
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Mr Jörn Warnecke (Nordita)03/05/2013, 10:30
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Friedrich Busse03/05/2013, 12:00
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Jonathan Braithwaite03/05/2013, 14:00
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Mark Miesch (High Altitude Observatory, National Center for Atmospheric Research, Boulder)SeminarOne of the leading paradigms to account for the 11-year solar activity cycle is the Babcock-Leighton (BL) dynamo model, whereby the principle source of mean poloidal field is attributed to the destabilization, rise, emergence, and dispersal of buoyant magnetic flux structures. Though the existence of sunspots and bipolar active regions is central to the operation of a BL dynamo, their...Go to contribution page
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Egor Illarionov (Moscow State University)TalkWe obtain the latitude-time distribution of the averaged tilt angle of solar bipoles. For large bipoles, which are mainly bipolar sunspot groups, the spatially averaged tilt angle is positive in the Northern solar hemisphere and negative in the Southern, with modest variations during course of the solar cycle. We consider the averaged tilt angle to be a tracer for a crucial element...Go to contribution page
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Delphine Hypolite (Research Institute in Astrophysics and Planetology (IRAP), Toulouse)TalkAims: We investigate the shape of the rotation profile of radiative stellar envelopes undergoing gravitational contraction to obtain a better understanding of the dynamics of such objects. Methods: We construct a model of a rotating core absorbing a baroclinic envelope enclosed in an undeformable spherical shell and solve the hydrodynamic equations using the Boussinesq...Go to contribution page
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Ana Borisova (Institute of Astronomy and NAO Rozhen, BAS)SeminarWe present analysis of the long-term photometric data of the active giant OP And. Our research is based on previously published photometric data, Hyparcos photometric series and observations obtained at Belogradchik observatory, Bulgaria. We provide Bayesian estimate photometric period of the star in the time interval 1983-1999 and compare it with the previous published ones. We have...Go to contribution page
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Thomas Hackman (Finnish Centre for Astronomy with ESO)TalkA basic method to measure the surface differential rotation on both the Sun and stars is to trace the movement of spots. The general notion is that spots on late-type stars are equivalents of sunspots. However, results from Doppler imaging and photometric time series analysis as well as numerical modelling have cast shadows of doubts on this assumption. It has been hard to observationally...Go to contribution page
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Leonid L. Kitchatinov (Institute for Solar-Terrestrial Physics, Irkutsk)SeminarInstabilities in stellar radiation zones are important for angular momentum transport, mixing of chemical species and, possibly, for dynamos. It is shown that even a very small radial differential rotation can lead to instability. Surfaces of constant density and constant pressure do not coincide in differentially rotating stars. The baroclinicity of stratification results in a...Go to contribution page
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Scott G. Gregory (School of Physics & Astronomy University of St Andrews)TalkA number of maps of the surface magnetic fields of newborn Sun-like stars have now been obtained using the technique of Zeeman-Doppler imaging. Their magnetic fields can be significantly more complex than a simple dipole, the usual assumption of models, and can vary markedly between sources. I will summarize the magnetic field topology information obtained to date and present...Go to contribution page
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Liyun Zhang (University of Oulu)TalkSolar active longitudes and their rotation have been studied for a long time using various forms of solar activity. However, the results on the long-term evolution of rotation rates and the hemispheric asymmetry obtained by earlier authors differ significantly from each other. We used a dynamic, differentially rotating reference system to determine the optimum values of the...Go to contribution page
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Reinhard Schlickeiser (Inst. f. Theoretische Physik, Ruhr-Universitaet Bochum)TalkMagnets have practically become everyday objects. Permanent ferromagnetism is a property of only a few densely packed materials, such as iron, in which the spin exchange interactions of individual atoms naturally line up in the same direction and create a residual persistent magnetic field. In the early universe, before iron and other magnetic materials had been created inside...Go to contribution page
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Alfio Bonanno (INAF, Osservatorio Astrofisico di Catania)TalkThe stability of a toroidal field in stellar radiation zone will be discussed by considering the combined effect of rotation, stable stratification and thermal conductivity. It will be shown that the influence of rotation depends on the magnetic configuration of the basic state. If the toroidal field increases sufficiently rapidly with the spherical radius, the instability cannot be...Go to contribution page
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Elena Benevolenskaya (Pulkovo Astronomical Observatory, Saint Petersburg)TalkIn this presentation I discuss the results of the detailed evolution of the solar active regions: NOAA 11101 during 10 days from 26 August 2010 to 4 September 2010 and NOAA 11106 from 12 September 2010 to 20 September 2010 using magnetic data of the line-of-sight component of the magnetic field and intensitygrams in continuum with 720 sec cadence. This period permits us to investigate...Go to contribution page
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Klaus G. Strassmeier (Leibniz-Institut fuer Astrophysik Potsdam (AIP))TalkI will discuss Doppler imaging (DI) and Zeeman-Doppler imaging (ZDI) techniques to map stellar magnetic fields and differential surface rotation and possibly meridional flows on cool stars. Emphasis will be on the techniques and their limitations but I will also highlight previous results and present some of our more recent DI and ZDI maps. An outlook is given for observing programs with...Go to contribution page
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Allan Sacha Brun (Laboratoire AIM Paris-Saclay, CEA/Irfu Université Paris)TalkWe will present our recent efforts to model G & K stars with the ASH code. We have designed new model coupling the convective envelope to a deep stable radiative interior. We have varied both the mass & rotation rates in order to pave a large parameter space and to derive scaling laws for these type of solar-like stars. We have also introduced seed magnetic field to study how dynamo action...Go to contribution page
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Elizabeth Cole (Department of Physics, University of Helsinki)TalkWe report the results from turbulent convection simulations in spherical wedges, keeping the density stratification fixed and varying the rotation rate. An upper limit to the Coriolis number that resulted in solar-like differential rotation is reported, above which the simulations exhibit almost-rigid rotation profiles. Adding a magnetic field into these rapid rotators within this...Go to contribution page
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Julien Morin (Institut für Astrophysik, Georg-August-Universität Göttingen)TalkM dwarfs are of prime interest for stellar dynamo theories. They indeed span a wide range of parameters, in terms of relative depth of the convection zone (the lowest-mass M dwarfs being fully convective) and rotation. The number of magnetic field measurements on M dwarfs has been rapidly growing in the past few years, trends are emerging and now need to be understood in the framework of...Go to contribution page
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Aditi Sood (School of Mathematics and Statistics, University of Sheffield)TalkA dynamic model of dynamo and rotation is investigated to understand the observational data of the dependence of the magnetic activities and the differential rotation \Delta \Omega on the rotation rate \Omega. Specifically, we propose a minimal seventh order non-linear dynamical system for magnetic fields and differential rotation \Delta \Omega by parameterizing the generation...Go to contribution page
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Gustavo Guerrero (Solar Physics, HEPL, Stanford University)TalkSolar and stellar activity is thought to be the result of the collective effects of turbulent-rotating convection. It develops large-scale flow patterns like differential rotation and meridional flows, induces the generation of magnetic fields as well as enhances their diffusion. In this work we explore the first part of the process, namely, the physic governing the development of the...Go to contribution page
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Santiago A. Triana (Institute of Astronomy, KU Leuven)TalkA 3-meter diameter liquid-metal spherical-Couette flow, composed of a rotating spherical container and a differentially rotating internal core, exhibits a sequence of sharp and strong inertial mode oscillations when the (inner core to outer sphere) rotation rate ratio is less than one or negative. At larger rotation ratios the flow exhibit bi-stable fluctuations. These observations are...Go to contribution page
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Mikkel Lund (Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Denmark)SeminarWith the launch of the Kepler spacecraft, long and uninterrupted time series have become available for a large variety of stars. These data are ideal for asteroseismic studies of the stars. As my PhD project I am studying how we can hope to use these data to infer properties on the differential rotation of solar-like star. I will discuss the current status of this project in addition...Go to contribution page
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Axel Brandenburg (Nordita)TalkOne of the original reasons for placing the solar dynamo at the bottom of the convection zone was the possibility of rapid loss of magnetic fields by magnetic buoyancy. In various simulations, however, turbulent pumping is often seen to be dominant. Other reasons for placing the dynamo at the bottom of the convection zone was that alpha would have a different (favorable) sign there, and...Go to contribution page
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Petri J. Käpylä (Department of Physics, University of Helsinki)TalkWe present results from three-dimensional simulations of rotating, magnetised, turbulent convection in spherical wedge geometry. We concentrate on the parameter regime where the differential rotation is solar-like, i.e. the equator rotates faster than the poles. We find that large-scale magnetic fields are generated within the whole convection zone. Many of the simulations show cyclic...Go to contribution page
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Yori Fournier (Leibniz-Institut fuer Astrophysik Potsdam (AIP))TalkThere is still a missing link in dynamo models between generating strong toroidal fields at the bottom of the convection zone and the sunspots as measures of activity. Since rotation is an important factor in the rise of magnetic flux through convection zones, we study the flux emergence under the influence of different rotation profiles. It is difficult to simulate realistic convection,...Go to contribution page
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Nicolas BESSOLAZ (University of Exeter)TalkMagnetic fields play an important role in the early evolution of young stars during the pre-main sequence phase. We present an investigation into the magnetic fields built by 3D convective dynamo action in such stars using the ASH code. We have extended our initial attempts to reproduce the magnetic field observed for BP Tau using spectropolarimetry (Bessolaz & Brun 2011) by computing a...Go to contribution page
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Leonid L. Kitchatinov (Institute for Solar-Terrestrial Physics, Irkutsk)TalkMeridional circulation is driven by non-conservative parts of the centrifugal and buoyancy forces. Each of the forces alone would drive a flow of hundreds meters per second. The forces, however, almost balance each other in the so-called thermal wind balance. The meridional flow results from slight deviation from the balance. The flow attains its largest velocities in the boundary layers...Go to contribution page
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Mark Miesch (High Altitude Observatory, National Center for Atmospheric Research, Boulder)TalkThe mean (axisymmetric) circulation in the meridional plane plays a key role in many recent solar and stellar dynamo models. This is particularly the case in so-called "Flux-Transport" dynamo models in which the meridional circulation regulates the duration of magnetic activity cycles. Many of these models are kinematic in nature so the meridional circulation must be prescribed. Yet,...Go to contribution page
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Manfred Kueker (Leibniz-Institut fuer Astrophysik Potsdam (AIP))TalkThe meridional flow is a key ingredient in the currently most favored model of the solar activity cycle, the flux transport dynamo. One major uncertainty in this model is the subsurface flow pattern, which is not yet sufficiently constrained by observations. We discuss the flows predicted by the mean field theory of stellar differential rotation for the Sun, lower main sequence stars, and giants.Go to contribution page
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Bidya Binay Karak (Department of Physics, Indian Institute of Science, Bangalore)TalkOne of the most striking aspects of the sunspot cycle is that there have been times in the past when sunspots did not appear for several years and a few cycles went missing. A most well-known example of this is the Maunder minimum during 1645-1715. Although reliable sunspot data did not exist before 1611, several indirect studies (C14 data from old tree rings and the Be10 data from...Go to contribution page
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Federico Spada (Leibniz-Institut fuer Astrophysik Potsdam (AIP))TalkA long-standing issue in the theory of low mass stars is the disagreement between the theoretical and observed mass-radius-Teff relationships. Stellar models systematically underpredict stellar radii by ~10% and overpredict effective temperatures at the ~5% level. Interestingly, the two effects compensate each other to give approximately the same luminosity, suggesting a surface origin for...Go to contribution page
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Igor Rogachevskii (Ben-Gurion University, Beer Sheva, Israel)TalkWe discuss an analytic theory for a new scaling for the alpha effect in turbulence with large Reynolds numbers and slow rotation. Using this theory and direct numerical simulations of slowly rotating stratified turbulence, we show that the alpha effect responsible for the generation of astrophysical magnetic fields is proportional to the logarithmic gradient of kinetic energy density...Go to contribution page
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Igor Rogachevskii (Ben-Gurion University of the Negev, Beer-Sheva)SeminarWe discuss a new theory of differential rotation in anisotropic density stratified inhomogeneous turbulent convection. A key point of this theory is an effect of the turbulent heat flux on the Reynolds stresses in a rotating turbulent convection. We solved a coupled system of dynamical equations which includes the equations for the Reynolds stresses, the entropy fluctuations and...Go to contribution page
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Michael Mond (Ben-Gurion University, Beer Sheva, Israel)TalkA new non-dissipative mechanism is proposed for the saturation of the axisymmetric magneto-rotational (MRI) instability in thin Keplerian disks that are subject to an axial magnetic field. The proposed mechanism relies on the energy transfer from the MRI to stable magnetosonic (MS) waves. A second order Duffing-like amplitude equation for the initially unstable MRI modes is derived. The...Go to contribution page
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Klaus-Peter Schröder (Universidad de Guanajuato)TalkWe studied the evolutionary age and mass of the solar-type MS stars of the sample described by Baliunas et al. 1995, of the Mt. Wilson CaII monitoring programme. Organized by subsamples of stars with strong and chaotic, moderate (clyclic or not), and low or absent activity, the activity strength (mean S-value) and characteristics show a very clear correlation with relative MS age....Go to contribution page
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Ansgar Reiners (Georg-August Universität, Institut für Astrophysik, Göttingen)TalkMagnetic dynamos are known to operate in sun-like and fully convective stars. Our conceptual models of dynamos produce predictions for stellar properties, among them rotation and angular momentum evolution, the generation of magnetic fields, non-thermal emission, and stellar activity cycles. I review the observational evidence for magnetic dynamos in low-mass stars and collect arguments...Go to contribution page
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Ludovic Petitdemange (MAG(CNRS/ENS/IPGP), LRA, Ecole Normale Supérieure, Paris)TalkMagnetic fields of low-mass stars and planets are thought to originate from self-excited dynamo action in their convective interiors. Observations reveal a huge variety of stellar and planetary magnetic fields that differ in their field strength and topologies. We try to better understand the conditions responsible for this diversity by means of numerical dynamo simulations. In a...Go to contribution page
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Matteo Cantiello (Kavli Institute for Theoretical Physics, University of California)TalkRecent observations have revealed the presence of both pulsations and magnetic fields in massive stars. As these phenomena can directly affect the mass-loss and the rotation rate, their impact on stellar evolution is potentially huge, with consequences for the final fate of massive stars. I will review some of the latest observational and theoretical developments in the field, focusing in...Go to contribution page
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Dmitry Sokoloff (Moscow State University)TalkWe study activity waves of the kind that determine cyclic magnetic activity of various stars, including the Sun, as a more general physical rather than a purely astronomical problem. We try to identify resonances which are expected to occur when a mean-field dynamo excites waves of quasi-stationary magnetic field in two distinct spherical layers. We isolate some features that can be...Go to contribution page
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Dmitry Sokoloff (Moscow State University)TalkDuring a solar magnetic field reversal the magnetic dipole moment does not vanish, but migrates between poles, in contradiction to the predictions of mean- field dynamo theory. We try to explain this as a consequence of magnetic fluctuations. We used the statistics of fluctuations to estimate observable signatures. Simple statistical estimates, taken with results from...Go to contribution page
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Timo Reinhold (Institute for Astrophysics Goettingen)TalkThe Kepler space telescope monitors more than 160.000 stars with an unprecedented precision providing the opportunity to study stellar variability of thousands of stars. We present rotation periods for thousands of active stars in the Kepler field. In most cases a second period close to the rotation period has been detected which is considered as hint for surface Differential Rotation...Go to contribution page
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Kwing L. Chan (Department of Mathematics, Hong Kong University of Science & Technology)TalkRotation exerts very significant effects on convection zones of stars. The phenomenology consists of two types: differential rotation and large‐scale long‐lived vortices. Both types exhibit prominently in outer planets of our solar system; these planets possess outer convective layers and rotate fast. Differential rotation appears in the form of multiple wind bands on Jupiter and Saturn,...Go to contribution page
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Matthew Browning (University of Exeter)TalkMost stars in our galaxy are smaller than the Sun. More than half (by number) are M-dwarfs, stars less than half as massive as the Sun and ten to a thousand times less luminous; below about spectral type M3.5, these stars are convective throughout their interiors. We examine the differential rotation and magnetism that may be realised in such stars, using 3-D MHD simulations with the...Go to contribution page
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Joern Warnecke (NORDITA, KTH Royal Institute of Technology and Stockholm University)TalkWe report on the results of three convective dynamo simulations with an outer coronal layer. The magnetic field is self-consistently generated by the convective motions beneath the surface. Above the convection zone we include a polytropic layer that extends to 1.6 solar radii. The temperature increases in this region to \approx8 times the value at the surface, corresponding to \approx 1.2...Go to contribution page
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Christoffer Karoff (Aarhus University, Department of Physics and Astronomy)TalkSince the launch of the Kepler spacecraft in 2009 we have monitored 20 Sun-like stars in the Kepler field-of-view for excess flux with the FIES spectrograph on the Nordic Optical Telescope. These 20 stars were selected based on their asteroseismic properties to sample the parameter space around the Sun and cover both sides of the Vaughan-Preston gap. The ultimate goal of this is to be...Go to contribution page
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Rafael A. Garcia Garcia (Laboratoire AIM, CEA/DSM-CNRS-Université Paris)TalkContinuous photometric coverage of stars provided by asteroseismic space missions, are a great opportunity to study their surface rotation and stellar variability. In particular, long and uninterrupted Kepler observations of more than 3.5 years allows us to study stellar activity cycles of many stars. A surface stellar activity proxy can be built from the variance of the light curve as the...Go to contribution page
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Dieter Schmitt (Max-Planck-Institut für Sonnensystemforschung, Lindau)TalkThe velocity and magnetic fields are well-known on the solar surface. Surface flux transport models describe the evolution of the magnetic field after emergence on the surface under the action of differential rotation, meridional circulation and turbulent magnetic diffusivity. Especially the polar field and the Sun's open flux are determined by the surface distribution of the magnetic...Go to contribution page
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Elena Benevolenskaya (Pulkovo Astronomical Observatory, Saint Petersburg)TalkThe current solar cycle 24 attracts an attention of researchers to study the nature of the solar activity at the different levels of the Sun from the interior to the solar corona. The Solar Dynamics Observatory (SDO) provides us multi-waves data from the Extreme Ultraviolet to the visible light and magnetic field measurements. Here, it is presented the synoptic structure of the solar cycle...Go to contribution page
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Rainer Arlt (Leibniz Institute for Astrophysics Potsdam)TalkBased on the sunspot drawings of Johann Staudacher made in 1749-1799, we derive the solar differential rotation for a period shortly after the Maunder minimum. A Bayesian analysis provides us with the full probability distribution for the unknowns, whence their uncertainties. The study demonstrates how valuable historical observations can be for today's astrophysics.Go to contribution page
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Jon Braithwaite (Argelander Institut für Astronomie, Universität Bonn)TalkThe Tayler instability appears in stars with predominantly toroidal magnetic fields. It is thought to be particularly relevant in the case of differentially-rotating radiative zones where the toroidal component of any seed field will be amplified. I shall present results from numerical simulations where the effects of magnetic diffusivity, rotation, and a weak poloidal field are...Go to contribution page
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Jyri Lehtinen (University of Helsinki)TalkOne popular method for detecting and quantifying surface differential rotation of active stars has been to monitor how the periods of their observed light curves fluctuate over time. The observed period fluctuations should indicate major spotted areas situated at different latitudes that have different rotation periods. The period determination of the light curves becomes, however,...Go to contribution page
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Gibor Basri (Astronomy Department, Univ. of California, Berkeley)TalkThe Kepler Mission has opened a whole new volume of parameter space in the realm of stellar photometry. It combines unprecedented precision with unprecedented long and complete time coverage, for well over 100,000 stars throughout the HR diagram. In particular it is very sensitive to starspots, with complete phase coverage over many rotation periods. This affords us the opportunity to...Go to contribution page
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Oleg Kochukhov (Department of Astronomy and Space Physics, Uppsala University)TalkZeeman Doppler imaging is the only observational method capable of providing spatially resolved maps of stellar magnetic fields. This technique is routinely used to reconstruct magnetic field topologies in different types of active stars. Recently ZDI of cool stars was improved to include a more realistic treatment of the polarised radiative transfer and a self-consistent modelling of the...Go to contribution page
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