Iqbal Ahmad Ansari, Aligarh Muslim University, India
Effect of Variability of Solar Wind on Low Latitude Pc3 Geomagnetic Pulsations in South-East Australia (Talk -> Poster)
Pc3 Geomagnetic pulsations are quasi-sinusoidal variations in the earth's magnetic field in the period range 10-45 seconds. The magnitude of these pulsations ranges from fraction of a nT(nano Tesla) to several nT. These pulsations can be observed in a number of ways. However the application of ground based magnetometer arrays has proven to be one of the most successful methods of studying the spatial structure of hydromagnetic waves in the earth's magnetosphere.The solar wind provides the energy for the earth's magnetospheric processes. Pc3-5 geomagnetic pulsations can be generated either externally or internally with respect to the magnetosphere. The Pc3 studies undertaken in the past have been confined to middle and high latitudes. The spatial and temporal variations observed in Pc3 occurrence are of vital importance because they provide evidence which can be directly related to wave generation mechanisms both inside and external to the magnetosphere. At low latitudes (L < 3) wave energy predominates in the Pc3 band and the spatial characteristics of these pulsations have received little attention in the past.An array of four low latitude induction coil magnetometers was established in south-east Australia over a longitudinal range of 17 degrees at L=1.8 to 2.7 for carrying out the study of the effect of the solar wind velocity on these pulsations. Digital dynamic spectra showing Pc3 pulsation activity over a period of about six months have been used to evaluate Pc3 pulsation occurrence. Pc3 occurrence probability at low latitudes has been found to be dominant for the solar wind velocity in the range 400-700 Km/sec. The results suggest that solar wind controls Pc3 occurrence through a mechanism in which Pc3 wave energy is convected through the magnetosheath and coupled to the standing oscillations of magnetospheric field lines. In conclusion it has been demonstrated that he occurrence probability of Pc3 pulsations depends on solar wind velocity with a threshold at about 320 km/sec and ranging up to 700 km/sec. It is likely that an instability originating from the direct interaction between the solar wind and the magnetosphere is exciting Pc3 pulsations through bow-shock associated waves.

Rainer Arlt, Astrophysikalisches Institut Potsdam
The magnetic stability of the solar tachocline
The stability of toroidal magnetic fields in the solar tachocline is investigated. We find an upper limit 1000 G for the field strength in the tachocline.

Horst Balthasar, Astrophysikalisches Institut Potsdam
Daily Sunspot Numbers and Periods of the Solar Rotation
Active longitudes on the sun have been searched for since long, and published results are controversial. This question recently became more important when active longitudes were found on other stars. In this contribution I investigate the daily sunspot relative numbers. They represent an integral measure of solar activity available for a long time interval.
A search for periodicities is performed with the classical Fast Fourier Transform, with a wavelet analysis and with the tool of superimposed epochs. The FFT yields a hump of power peaks near the synodic rotation period of 27 days, but only a very weak and insignificant enhancement around 13.5 days. This result indicates that the mean rotational variation of the sunspot numbers has typically one maximum and one minimum (overlaid by minor fluctuations). The wavelet analysis shows that power for single periods show up for certain time intervals and then they disappear. A systematic drift during the solar activity cycle, as it is expected if the pattern follows a differential rotation law, is not detected. Similar results are obtained from the superimposed epochs. Periodic ``flip-flops'' with time scales of a few years as for some stars are not found in this investigation for the sun.
The rotation of the sunspots might reflect the internal rotation of the sun, but it fits better to the range of highest rotation rates in the upper convection zone than to the rotation near the tachocline.

Jacques Beckers, National Solar Observatory
Can Variable Meridional Flows Lead to False Exoplanet Detections?
The search for habitable exoplanets centers on the search for planets in Earth-like orbits around Sun-like stars. Radial velocity searches for these planets require precisions of 1 m/sec and smaller. At these precisions stellar surface motions might lead to false detections. Of particular interest are variable meridional flows at the stellar surface. I will review the available observational material of solar surface meridional flows using both Doppler shift and local helioseismology observations. Interpretation in terms of Doppler shifts in integrated sunlight leads to estimates of the likelihood of false detections. As a result of this "thinkshop" I hope to expand the results to a more general stellar context which includes different stellar rotation rates, masses, diameters, spectral types and activity cycle periods.

Elena Benevolenskaya, Stanford University
Magnetic elements in Polar Regions on the Sun
Using the Michelson Doppler Imager (MDI) data from Solar and Heliospheric Observatory (SOHO), the rotation rate of the unipolar magnetic regions in North high-latitude regions of the Sun isestimated by tracking individual magnetic elements. The analysisreveals a strong speed down near the pole, which is greater than the Doppler and magnetic rotation rates estimated by Snodgrass and Ulrich (1990), and rotation rate inferred from helioseismology (Birch and Kosovichev, 1998).

Svetlana Berdyugina, ETH Zurich
Stellar butterfly diagrams and differential rotation
The solar butterfly diagram provides an important constraint for the dynamo theory. Analogous stellar diagrams have not been however widely used for such a purpose because of luck of data. Here I introduce a recently proposed method for recovering stellar butterfly diagrams, present a few examples for cool active stars and compare them with the solar case. I demonstrate how the butterfly diagram can be used to verify measurements of the stellar differential rotation.

Gennady Bisnovatyi-Kogan, Space Research Institute
Centrifugal driving of differential rotation in convective star regions.
Behaviour of convective elements in rotating stars depends on the direction of their eddies. It leads to equatorial acceleration in convective stellar envelope. Quantitative estimation for a value of such acceleration are done for the solar convective zone.

Alfio Bonanno, INAF-OACT
Stretching of the toroidal field and generation of magnetosonic waves in differentially rotating plasma
With V. Urpin
We consider the generation of magnetosonic waves in differentially rotating magnetized plasma. Differential rotation leads to increase of the azimuthal field by winding up the poloidal field lines into toroidal ones. An amplification of weak seed perturbations can occur on this time-dependent background state. The only necessary condition of this amplification is the presence of a non-vanishing component of the magnetic field in the direction of the angular velocity gradient. Consequences for the tachocline problem are discussed.

Jonathan Braithwaite, CITA, Toronto
Magnetic field configurations in rotating non-convective stars
3-D numerical MHD is used to explore the stability of equilibria in non-convective stars. Axisymetric poloidal and toroidal fields are looked at, as well as the effects of rotation and diffusivity. In addition, the hydrostatic approximation is employed in numerical MHD and used to study a differential-rotation driven dynamo.

Roman Brajsa, Hvar Obs., Faculty of Geodesy, Univ. of Zagreb
On the Solar Rotation and Activity
With H. Woehl (2), D. Ruzdjak (1), B. Vrsnak (1), G. Verbanac (3), L. Svalgaard (4), J.-F. Hochedez (5). (1) Hvar Observatory, Faculty of Geodesy, Univ. Zagreb,Croatia; (2) Kiepenheuer-Inst. für Sonnenphysik, Freiburg, Germany; (3) Geophysical Inst., Faculty of Science, Univ. Zagreb, Croatia; (4) Easy Toolkit, Inc., Houston, USA; (5) Obs. Royal de Belgique, Bruxelles, Belgium
The interaction between differential rotation and magnetic fields in the solar convection zone was recently modelled by Brun (2004). One consequence of that model is that the Maxwell stresses can oppose the Reynolds stresses, and thus contribute to the transport of the angular momentum towards the solar poles, leading to a reduced differential rotation. So, when the magnetic fields are weaker, a more pronounced differential rotation can be expected, yielding a higher rotation velocity at low latitudes taken on the average. This hypothesis is consistent with the behaviour of the solar rotation during the Maunder minimum. In the present contribution we search for similar signatures of the relationship between the solar activity and rotation determined tracing sunspot groups and coronal bright points. We use the extended Greenwich data set (1874-1981) and a series of full-disc solar images taken at 28.4 nm with the EIT instrument on the SOHO spacecraft (1998-2001). We investigate a dependence of the solar rotation on the solar activity (described by the relative sunspot number) and the interplanetary magnetic field (described by theinterdiurnal variability index). Special attention isdevoted to possible rotational signatures of a grand solaractivity minimum at the beginning of the 20th century.

Axel Brandenburg, Nordita
Location of the solar dynamo
The location of the solar dynamo is discussed in the context of new insights into the theory of nonlinear turbulent dynamos. It is argued that, from a dynamo-theoretic point of view, the bottom of the convection zone is not a likely location and that the solar dynamo may be distributed over the convection zone. The near surface shear layer produces not only east-west field alignment, but it also helps the dynamo disposing of its excess small scale magnetic helicity.

Benjamin Brown, University of Colorado, Boulder
Rapid Rotation, Active Nests of Convection and Global-scale Flows in Solar-like Stars
With M. Browning, A.S. Brun, M. Miesch, J. Toomre
Our sun must have rotated much more rapidly earlier in its life, as is suggested by observations of many rapidly rotating young solar-type stars. In these stars the deep convective envelopes and the dynamos operating there must sense the effects of rotation quite strongly. We have carried out extensive 3-D simulations of anelastic convection in spherical shells to study the effects of rapid rotation on deep stellar convection. In our more rapidly rotating suns, convection in the equatorial regions exhibits strong longitudinal modulation and at the fastest rotation rates convection is restricted to small active nests, with quiescent regions of streaming zonal flow inbetween. These nests of convection persist for long periods and drive a strong differential rotation.

Matthew Browning, UC Berkeley
Simulations of Dynamo Action in the Solar Convection Zone and Tachocline
We present results from global 3-D nonlinear simulations of magnetic dynamo action achieved by turbulent solar convection in a penetrative geometry. Our spherical computational domain encompasses both the bulk of the convection zone and a portion of the underlying stable region, where we have imposed a tachocline of rotational shear using both a hydrodynamic drag term and small entropy perturbations consistent with thermal wind balance. Thus we are able to assess several dynamical "building blocks" thought to play major roles in the operation of the global solar dynamo, including differential rotation arising from convection, magnetic pumping, and the stretching and amplification of toroidal fields within the tachocline. In the stable region, strong axisymmetric toroidal magnetic fields (about 3000 G in strength) are established, in contrast to the predominantly fluctuating fields realized within the bulk of the convection zone. The mean toroidal fields in the stable layer exhibit a striking antisymmetric parity akin to that observed in sunspots, with fields in the northern hemisphere almost entirely of the oppposite sign to those in the southern hemisphere. The overall polarity of the fields retains the same sense over much longer timespans than in prior simulations without a tachocline of shear.

Allan Sacha Brun, CEA-Saclay
MHD Instabilities in Stellar Radiation Zones With or Without Rotation
We present recent 3-D MHD simulations of the solar radiation zone and tachocline. We seek to answer several questions: Can a fossil field prevent the tachocline from spreading inward? Could the magnetic field topology in the radiation zone be purely toroidal or poloidal? How rotation and shear modifies the magnetic field topology found in radiation zone? Could MHD instabilities lead to dynamo action in differentially rotating radiative zone? We find that a purely dipolar field is unlikely to exist in the solar radiation zone because it undergoes a non axisymmetric instability of high m numbers, first identified by Tayler and collaborator in mid 70's. We also find that such a fossil field easily connects with the imposed latitudinal shear associated with the differential rotation of the solar convection envelope and lead to Ferraro's law of isorotation, thus resulting in a thick tachocline, which is at odd with helioseismic observations. Further the shearing of the fossil field by a large scale flow, when such flows are present in the radiation zone, leads to the formation of strong toroidal field that becomes unstable to m=1 type of instabilities. However as of today, we do not find dynamo action in radiation zone in our simulation, since the axisymmetric poloidal field decays away.

Dirk K. Callebaut, Phys. Dept., Univ. of Antwerp
Exact generation from multipolar seed field
The exact solution of the evolution equation for the magnetic field in ideal MHD is obtained provided the velocity has only an azimuthal component. Combining this with a multipolar seed field and the differential rotation of the Sun one may obtain fair results for both the polar faculae and the sunspots by the same mechanism. A natural gap between them is constituted by the conical blades in the solar convection zone where d(omega)/dr = 0. The delay of half a cycle by which the polar faculae precede the sunspots (according to observations of Makarov and co-workers) may be attributed to the equator-ward motion of the torsional oscillations.

Kwing Chan, Hong Kong University of Science and Technology
Rotating convection in f-boxes: faster rotation and larger boxes
Numerical results based on tens of cases that populate the parametric space rather densely are to be presented. New insights can be derived. New phenomena appear.

Andrew Collier Cameron, School of Physics and Astronomy
Differential rotation on rapidly-rotating stars
(to follow)

Mausumi Dikpati, National Center for Atmospheric Research
Predicting solar `climate' by assimilating magnetic data into a flux-transport dynamo
Observational and theoretical knowledge about global-scale solar dynamo ingredients have reached the stage that it is possible to calibrate a flux-transport dynamo for the Sun by adjusting only a few tunable parameters. The important ingredients in this class of model are differential rotation (Omega-effect), helical turbulence (alpha-effect), meridional circulation and turbulent diffusion. The meridional circulation works as a conveyor belt and governs the dynamo cycle period. Meridional circulation and magnetic diffusivity together govern the memory of the Sun's past magnetic fields. After describing the physical processes involved in a flux-transport dynamo, we will show that a predictive tool can be built from it to predict mean solar cycle features by assimilating magnetic field data from previous cycles. We will discuss the theoretical and observational connections among various predictors, such as dynamo-generated toroidal flux integral, cross-equatorial flux, polar fields and geomagnetic indices.

Detlef Elstner, Astrophysikalisches Institut Potsdam
Do axisymmetric ALPHA^2-dynamos exist?
Tbd

Francisco Espinosa Lara, Laboratoire d'Astrophysique de Toulouse et Tarbes
The dynamics of fully radiative rotating stars (Talk -> Poster)
The structure and dynamics of a fully radiative rotating star is solved in a two-dimensional grid using spectral methods which allows for a more efficient discretization that finite differences methods. We take into account the full effect of rotation and flatness of the star. We compute the differential rotation and meridional circulation stemming from the baroclinicity of the star in such radiatives zones, obtaining interesting results as, for example, that equatorial regions rotate faster than polar ones and the scaling of meridional circulation with Ekman number.

Nicholas Featherstone, JILA / APS University of Colorado at Boulder
Convective Core Dynamos of A-type Stars in the Presence of a Fossil Magnetic Field
The persistent magnetic fields of Ap stars are generally thought to be of primordial origin, but dynamo generation of magnetic fields may offer alternative possibilities. Deep within the interiors of such stars, vigorous core convection likely couples with rotation to yield magnetic dynamo action, generating strong magnetic fields. Recent numerical models suggest that a primordial field remaining from the star's formation may possess a highly twisted toroidal shape in the radiative interior. We have used detailed 3-D simulations to study the interaction of such a magnetic field with a dynamo generated within the core of a 2 solar mass A-type star. Dynamo action realized under these circumstances is much more vigorous than in the absence of a fossil field in the radiative envelope, yielding magnetic field strengths (of order 100 kG) much higher than their equipartition values relative to the convective velocities. We examine the generation of these fields, as well as their effect on the complex dynamics of the convective core.

Emese Forgács-Dajka, Eötvös University
Behaviour of sunspot polarities during the reversal of dynamo field direction (Poster)
With Z.T. Kiss
According to our present knowledge based on the recent solar dinamo models, the direction of the magnetic field reverses about every 11 years, causing the sunspot cycle as ropes of magnetic field lines emerge to the surface of the Sun and manifest as sunspots on the photosphere. Forgács-Dajka et al.(2004) found that the sequential Schwabe cycles overlap each other more and more in the secular time scale, but the behaviour of the reversal of the dynamo field direction could not be studied using the Greenwich Royal Observatory's sunspot data. In this work we examined the sunspots polarities using the NSO magnetic synoptic maps around the 11-year Schwabe minima as other possibility one can consider some additional stochastic phenomena in the solar dynamo.

Pascale Garaud, Baskin School of Engineering, UC Santa Cruz
Constraints on angular momentum transport in the Sun from simulations of the tachocline
With T. Rogers
I present new simulations of meridional flows in the solar interior, and study their role in establishingangular momentum balance in the radiative zone. Comparisons with observations set strict upper limits on the strength of meridional flows downwelling from the convection zone. A new model of the tachocline in the light of these results is presented.

Luiz Garcia de Andrade, UERJ
Riemannian geometry of nonplanar twisted current-carrying solar loops (Poster)
Curvature and torsion effects on current-carrying solar loops are obtained from soho data.

Gustavo Guerrero, IAG Universidade de Sao Paulo
The influence of the shape and the thickness of the solar tachocline in the latitudinal distribution of the toroidal magnetic fields in the solar dynamo
Flux-dominated solar dynamo models, which resolve the MHD induction equation in 2D, have demonstrated to be quite successful at reproducing most of the observed features of the large-scale solar magnetic cycle, but generally produce an inappropriate latitudinal distribution of the toroidal magnetic fields, showing fields of large magnitude at high latitudes where sunspots are not observed. This problem has been previously examined with apparently good results by allowing a deep meridional flow of matter. However, this approximation generates other kind of problems concerning to the mixing theory and the angular momentum transport. Here we treat the same problem from a different approach: assuming a kinematical solar dynamo model, we explore the contributions of both the radial and the latitudinal shear terms in the generation of the toroidal magnetic field and vary the shape and the thickness of the solar tachocline. We find that, contrary to what was usually assumed in previous models, the latitudinal component is always dominant over the radial component at producing toroidal field amplification. These results are sensitive to the adopted diffusivity profile, specially in the inner convection zone. In a detailed parameter analysis we estimate the different regimes in which the toroidal magnetic field appears in the appropriate latitudes as a function of the thickness of the solar tachocline and the magnetic diffusivity coefficient in the convection layer. Our results support tachoclines with widths either smaller than or of the order of 0.02 solar radius, or larger than or equal to 0.08 solar radius. Intermediate values are discarded. We have also found that a prolate tachocline is able to reproduce solar-like butterfly diagrams depending on the choice of appropriate diffusivity profiles and tachocline width range.

Mandy Hagenaar, Lockheed Martin Solar and Astrophysics Labs
Ephemeral Bipolar Regions in Coronal Holes (Poster)
Coronal Holes are characterized by the presence of a large region of unipolar magnetic field. Several studies have found that the evolution of magnetic flux is much faster in quiet Sun regions without coronal holes than in regions with coronal holes. This is equivalent to the finding that coronal holes form where the emergence of new magnetic flux is a local minimum. We study 6 SOHO/MDI sequences that show one or more coronal holes in SOHO/EIT. We study the density of magnetic network concentrations and the possible difference between the distributions of the two polarities. We discuss our findings and the implications for the flux emergence rate in- and out-side coronal holes.

Volkmar Holzwarth, Max-Planck-Institut fuer Sonnensystemforschung
The impact of meridional circulation on stellar butterfly diagrams and polar caps
With Duncan Mackay, Moira Jardine (Univ. St Andrews)
Observations of rapidly rotating solar-like stars show a mixture of opposite-polarity magnetic fields within their polar regions. To explain these observations, models describing the surface transport of magnetic flux demand the presence of fast meridional flows. We link sub-surface and surface magnetic flux transport simulations to investigate the impact of meridional circulations on the latitudinal eruption pattern of magnetic flux tubes and the influence of the resulting butterfly diagrams on polar magnetic field properties. Prior to their eruption, magnetic flux tubes experience an enhanced latitude-dependent poleward deflection through meridional flows, which renders the wings of stellar butterfly diagrams distinctively convex. The subsequent evolution of the surface magnetic field shows that the increased number of newly emerging bipoles at higher latitudes promotes the intermingling of opposite polarities of polar magnetic fields. The associated magnetic flux densities are about 20% higher than in the case disregarding the pre-eruptive deflection, which eases the necessity for very fast meridional flows predicted by previous investigations.

Swetlana Hubrig, ESO
Evolution of Magnetic Fields in Stars Across the Upper Main Sequence
With P. North, M. Schöller
We re-discuss the evolutionary state of upper main sequence magnetic stars and the observed distribution of the magnetic field geometry using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and definitely determined longitudinal magnetic fields. Knowledge of the evolution of the magnetic field and its geometry, especially of the distribution of the obliquity angle $\beta$ (the orientation of the magnetic axis with respect to the rotation axis) is essential to understand the physical processes taking place in these stars and the origin of their magnetic fields (fossil versus contemporary dynamo).

Swetlana Hubrig, ESO
Spots on the surface of HgMn stars: clues to the origin of Hg and Mn peculiarities. (Poster)
With J.F. González
We will present the results of our recent survey of the inhomogeneous distribution of various elements on the surface of Bp stars with Hg and Mn peculiarities. Further, we will discuss the mechanisms that could be responsible for the development of the chemical anomalies in these stars.

Emre Isik, Max Planck Institute for Solar System Research
A coupled model of magnetic field generation and transport in stars
We have developed a three-part model of magnetic field generation and transport for the Sun and rapidly rotating Sun-like stars. We use the latitude-time distribution of the toroidal component of magnetic field provided by a thin-layer mean-field dynamo as initial values for field strengths of toroidal flux tubes at the bottom of the convection zone. The field strengths and latitudes of emerging flux tubes are selected with a probability proportional to the corresponding growth rate of Parker instability. Following the rise of each unstable flux tube, the emergence latitudes and tilt angles are determined and used as input for a surface flux transport model. The properties for activity cycles are discussed for the case of the Sun and for other stars.

Silva Järvinen, Astrophysikalisches Institut Potsdam
Doppler Imaging of V889 Her (Poster)
We present four Doppler images of a young active dwarf V889 Hercules. These previously unpublished maps are compared with other Doppler maps of this star. Together with the previously published maps, the new surface images cover the whole photometric cycle. This allows us to study the spot evolution on V889 Her in detail over a full photometric cycle.

Sonja Jejcic, University of Ljubljana
The Improvement of Solar Optical instrument at Ljubljana Observatory (Poster)
The improvement of the spectroscopic instrument at Ljubljana observatory will open a possibility of new measurements of solar rotation. This study presents the improvement of the instrument and preliminary results of solar rotation measured by the Doppler shift of Fraunhofer lines calibrated by the telluric water lines. New solar rotation coefficients are compared with those made before the changes. A synthetic spectrum surrounding Fraunhofer lines is also presented.

Laurène Jouve, CEA Saclay/DSM/DAPNIA/Service d'astrophysique
On the role of meridional flows in flux-transport dynamo models
Inspired by recent observations and 3D simulations that both exhibit multicellular flows in the solar convection zone, we seek to characterize the influence of various profiles of circulation (1 large single cell, 2 cells in radius and 4 cells per hemisphere) on the behaviour of solar mean-field dynamo models. We focus our study on few specific points: the role played by these flows in setting the cycle period and the shape of the butterfly diagram and their influence on the magnetic field parity selection. We confirm that adding cells in latitude tends to speed up the dynamo cycle whereas adding cells in radius more than triples the period. Moreover, our studies show that adding cells in radius or in latitude seems to favor the parity switching to a quadrupolar solution. According to our numerical models, the observed 22-yr cycle and dipolar parity is easily reproduced by models including multicellular meridional flows. On the contrary, the resulting butterfly diagram and phase relationship between the toroidal and poloidal fields are affected to a point where it is unlikely that such multicellular meridional flows persist for a long period of time inside the Sun, without having to reconsider the model itself. We will also present the results of an international dynamo benchmark which validates the code used in these simulations.

Petri Käpylä, Nordita
Turbulent viscosity and Lambda-effect from direct turbulence simulations
With A. Brandenburg
Turbulent fluxes of angular momentum, also known as the Reynolds stresses, are considered to be one of the main ingredients in generating differential rotation and meridional flows in convective stellar envelopes. During the past few years, a lot of effort has been spent in computing these fluxes from sophisticated numerical models of convection. These models have revealed some surprising results, such as latitudinal momentum flux peaking very sharply near the equator and a radially outward directed flux for rapid enough rotation. Given that these results remain somewhat inconclusive it is useful to study a more simple system where the different effects can be more easily disentangled.
In the present study, the diffusive (turbulent viscosity) and non-diffusive (Lambda-effect) contributions to the Reynolds stress are determined from homogeneous numerical models of turbulence under the influence of large scale shear and rotation, respectively. In order to concentrate specifically on these effects, stratification and heat flux are neglected. The additional anisotropy required for the Lambda-effect to occur is obtained either via anisotropic forcing or via a large scale shear. Comparisons are made with earlier results from 3D convection models and an analytical closure model introduced by Ogilvie (2003, MNRAS, 340, 969).

Alexander Kholtygin, Astronomical Institute, Saint-Petersburg Uni
Line profile variability of OB stars: pulsation, rotation and magnetic field
Variability of line profiles in spectra of bright OB stars have been studied. We obtain more than 1000 spectra high quality spectra of delta Ori A, lambda Ori A, alpha Cam, 19 Cep, iota Her, rho Leo and other targets. For all observed stars the line profile microvariability (lpv) of the small amplitude 0.5-2% was revealed. For most stars only cyclic components of lpv at the time scales from hours to days were detected. These components appeared to be connected both with the non-radial pulsations (NRP) and rotation line profile modulation. Both p and g modes of NRP were seen. The cyclic lpv of the emission line CIII 5696 in spectra of delta Ori A and lambda Ori A were discovered for the first time. We found the evidences of the stochastic lpv in the spectra of lambda Ori A probably connected with the small clunps in the stellar wind. The impact of moderate magnetic field (100-1000 G) on the lpv and the stucture of stellar atmospheres was investigated.

Alexander Kholtygin, Astronomical Institute, Saint-Petersburg Uni
Magnetic field of rho Leo: discovery, generation and stability (Talk -> Poster)
We report the results of searching the magnetic field of the bright B1I supergiant rho Leo. The star was observed in 2004-2006 at the Northern Caucasus 6-meter Telescope Special Astrophysical Observatory (SAO) and Bohyunsan Optical Astronomy Observatory (South Korea) in 2004. Approximately 100 spectra of stars with high temporary resolution (2-7 minutes) and spectral resolution from 15000 to 60000 were obtained. A very high signal to noise ratio up to 2000 was achieved. We reveal the weak microvariability of the hydrogen, helium and ionized silicium line profiles in spectra of the star. The relation of the detected variability with the non-radial pulsation of the star have been proposed. The SAO observation in 2005 and 2006 was made with using the circular polarization analyzer. Frome those we found the evidences of the weak magnetic field of rho Leo with dipole geometry and the polar value about of 250 G. We discuss the possible generation mechanismas of the field and incline to the fossile nature of the rho Leo field. The long-term stability of the fossil early-type stars magnetic field and the generation of the field in a result of dynamo action are discussed.

Leonid Kitchatinov, Institute for Solar-Terrestrial Physics
Hydromagnetic stability of stellar radiative cores with toroidal magnetic fields
Linear stability of rotating radaitive core containing toroidal magnetic field is concerned. It is argued that radial scales of unstable disturbances should be short to minimize the stabilizing effect of subadiabatic stratification. Linear equations are derived for weak disturbances of magnetic and velocity fields which are global in horizontal dimensions but short-scaled in radius. Stability is estimated by solving eigenvalue problem for the equations. The magnetic instability in the case of rigid rotation is essentially three-dimensional. It does not exist in a 2D formulation with strictly horizontal disturbances on decoupled spherical shells. Only stable (magnetically modified) r-modes are found in this case. The instability recovers in 3D. The most rapidly growing modes for the Sun have radial scales smaller than 1 Mm. The finite thermal conductivity makes a strong destabilizing effect. The marginal field strength for the onset of the instability in the upper part of the solar radiative zone is about 600~G. The toroidal field can only slightly exceed this critical value for otherwise the radial mixing produced by the instability would be too strong to be compatible with the observed lithium abundance. Also the threshold for hydrodynamic instability of differential rotation which exists in 2D is lowered in 3D. When radial displacements are included, the value of 28% for critical shear is reduced to 21%. Estimations of joint instability of toroidal field and differential rotation shows that steady axisymmetric solutions for solar tachocline configured by magnetic field are stable against nonaxisymmetric disturbances.

Heidi Korhonen, Astrophysikalisches Institut Potsdam
From flip-flop dynamo models to observation
In many active stars the spots concentrate on two permanent active longitudes which are 180 degrees apart. In some of these stars the dominant part of the spot activity changes the longitude every few years, creating the so-called flip-flop phenomenon. In this work we present dynamo models that are able to reproduce this behaviour, and investigate the long-term photometric behaviour based on these models. We have also investigated a sample of active stars to find more objects showing this intriguing phenomenon, with the aim of creating a statistically significant sample of flip-flop stars.

Alexander Kosovichev, Stanford University
Helioseismology measurements of variations of the differential rotation and meridional flows
The Sun's differential rotation and meridional flows hold the key to understanding the basic mechanisms of solar activity. They provide important input parameters for dynamo models, and their variations with the solar activity cycle reflect dynamics of subsurface magnetic fields, which are difficult to detect directly by helioseismology. Helioseismology observations from the SOHO space mission and GONG network have allowed us to monitor the variations of the differential rotation and meridional flow during the whole 11-year activity cycle. They provided important clues and constraints for dynamo theories. However, new puzzles emerged, and the global magnetohydrodynamics of the Sun is far from understanding. I present a review of the observational results obtained by global and local helioseismology, and attempts to explain these.

Zsolt Kövári, Konkoly Observatory
Anti-solar differential rotation with poleward meridional flow on the K1-giant sigma Geminorum (Poster)
With J. Bartus, K. Vida, M. Svanda, E. Forgács-Dajka, K.G. Strassmeier, K. Oláh
We revise and refine our previous result on recovering the spot migration pattern of the long-period RS CVn-type binary sigma Gem from time-series Doppler images (K\H{o}v\'ari et al. 2001, A&A 373, 199). Using the technique ACCORD (Average Cross-CORrelation of contiguous Doppler images) for our set of Doppler images covering 3.6 consecutive rotation cycles, we find a conclusive result suggesting anti-solar differential rotation with a shear of alpha~0.02. We also derive poleward drift with an average speed of a few hundred m/s. We apply local correlation tracking technique (LCT) on the same data and find a confirming result.

Manfred Küker, Astrophysikalisches Institut Potsdam
Modelling differential rotation in F stars
We model stellar differential rotation based on the mean-field theory of fluid dynamics. DR is mainly driven by Reynolds stress, which is anisotropic and has a non-diffusive component because the Coriolis force affects the convection pattern. Likewise, the convective heat transport is not strictly radial but slightly tilted towards the rotation axis. That causes the polar caps to be slightly warmer than the equator. This drives a flow opposite to that caused by differential rotation and so allows the system to avoid the Taylor-Proudman state. Our model reproduces the rotation pattern in the solar convection zone and allows predictions for other stars with outer convection zones. The strength of the differential rotation turns out to depend mainly on the spectral type and only weakly on the rotation rate. We present results for a range of spectral types, including F and A, which show signs of very strong differential rotation in some cases. Stars close to the convection limit have shallow convection zones. Consequently, the convective turnover times are short and fast rotation is needed to reach Coriolis numbers similar to that in the solar convection zone. We thus find solar-type rotation and meridional flow patterns at much shorter rotation periods and horizontal shear much larger than on the solar surface, in agreement with recent observations.

Antonino Francesco Lanza, INAF-Osservatorio Astrofisico di Catania
Modelling the time variations of the surface differential rotation in AB Dor and LQ Hya
Sequences of Doppler images of the young, rapidly rotating late-type stars AB Dor and LQ Hya show that their equatorial angular velocities and the amplitudes of their surface differential rotation vary versus time. Such variations can be modelled, by assuming that the internal angular velocity is uniform over cylindrical surfaces co-axial with the rotation axis, to obtain information on the intensity of the magnetic stresses within the stellar convection zone (Lanza 2006, MNRAS 373, 819). Here we show that similar results can be found by means of a more general model that does not introduce any assumption on the internal angular velocity, but assumes that the magnetic stresses responsible for the angular velocity variations are localized in a thin shell close to the base of the convection zone (Lanza, 2007, AA submitted).

Nicolas Leprovost, University of Sheffield
Theory of turbulent mixing and transport in the Sun
With E.-J. Kim
Turbulent transport plays a crucial role in the mixing and angular momentum transport in the sun and stars. Here, we report on the theory of turbulent mixing and transport by taking into account the effects of (global) rotation and sheared flow (provided by differential rotations). By solving quasi-linear equations for the fluctuating fields, we derive turbulence amplitude and turbulent transport coefficients (turbulent viscosity and diffusivity), taking into account the complex interplay among turbulence, rotation, and shear flows. Specifically, the interaction between the shear and the rotation is shown to give rise to a novel non diffusive flux of angular momentum (known as the Lambda effect), possibly offering a mechanism for the occurrence of a strong shear region in the sun. Furthermore, we elucidate the role of global and differential rotations in regulating turbulence and inducing anisotropic turbulence. The effects of density stratification and magnetic fields and the implications of our results for the mixing and transport in the solar tachocline/convection zone will further be discussed.

Stephen Marsden, Anglo-Australian Observatory
Starspots and Relativity: Applied Doppler imaging for the Gravity Probe B mission
Gravity Probe B (GP-B) is a satellite experiment designed to verify two predictions of Einstein's theory of general relativity, the geodetic effect and "frame-dragging". The experiment is based on measuring gyroscope drift with respect to the optical centroid of the satellite's guide star, the single-lined spectroscopic binary IM Pegasi. IM Peg was chosen as it is bright in both the optical and radio bands, however the star is magnetically active with dark spot features covering 10% or more of the stellar surface. The requested standard error for the experiment of 0.5 milliarcseconds per year implies that even small contributions to the shift of the optical centroid of IM Peg must be determined. In support of the GP-B mission, we were asked to undertake an intensive Doppler imaging survey of the primary, K giant, component of IM Peg to determine the effect of the primary's spot features on the optical centroid of the system. High-resolution echelle observations of IM Peg were obtained on an almost nightly basis (when possible) for nearly 3 years, with over 30 surface images of the primary being reconstructed. This presentation gives an overview of the results from this Doppler imaging project.

Stéphane Mathis, CEA/DSM/DAPNIA/SAp
Meridional circulation in the radiation zones of rotating stars: origins, behaviors and consequences on stellar evolution
Stellar radiation zones are the seat of meridional currents. This circulation has a strong impact on the transport of angular momentum and the mixing of chemicals that modify the evolution of stars. First, we recall in details the dynamical processes that are taking place in differentially rotating stellar radiation zones and the recent theoretical advances we have achieved in the modelling of the meridional circulation. Then, we present our new results of numerical simulations which allow us to follow in 2D the secular hydrodynamics of rotating stars, assuming that anisotropic turbulence enforces a shellular rotation law and taking into account the transport of angular momentum by internal gravity waves. The different behaviors of the meridional circulation in function of the type of stars which is studied is discussed in details with their physical origin and their consequences on the transport of angular momentum and of chemicals. Finally, we show how this work is leading to a dynamical vision of the evolution of rotating stars from their birth to their death.

Travis Metcalfe, High Altitude Observatory, NCAR
Asteroseismic signatures of stellar magnetic activity cycles
Observations of stellar activity cycles provide an opportunity to study magnetic dynamos under many different physical conditions. Space-based asteroseismology missions will soon yield useful constraints on the interior conditions that nurture such magnetic cycles, and will be sensitive enough to detect shifts in the oscillation frequencies due to the magnetic variations. We derive a method for predicting these shifts from changes in the Mg II activity index by scaling from solar data. We demonstrate this technique on the solar-type subgiant beta Hyi, using archival International Ultraviolet Explorer spectra and two epochs of ground-based asteroseismic observations. We find qualitative evidence of the expected frequency shifts and predict the optimal timing for future asteroseismic observations of this star.

Mark Miesch, High Altitude Observatory, NCAR
Differential Rotation and Meridional Circulation in Global-Scale Simulations of Solar Convection
With A.S. Brun, J. Toomre, and M.L. DeRosa
In the convection zone of the Sun in and other stars, differential rotation and meridional circulations are maintained via the redistribution of momentum and energy by convective motions. In order to properly capture such processes in a numerical model, the correct spherical geometry is essential. In this talk I will review recent insights into the maintenance of mean flows in the solar interior obtained from high-resolution simulations of solar convection in rotating spherical shells. Coriolis forces induce Reynolds stresses which transport angular momentum equatorward and they also yield latitudinal variations in the convective heat flux. Meridional circulations induced by baroclinicity and rotational shear further redistribute angular momentum and alter the mean stratification. This gives rise to a complex nonlinear interplay between turbulent convection, differential rotation, meridional circulation, and the mean specific entropy profile. Thermal and mechanical coupling to the radiative interior via the tachocline also plays a role in determining the rotation and circulation patterns which are realized. I will describe how this drama plays out in our simulations and what implications it has for solar and stellar activity.

Urmila Mitra-Kraev, University of Sheffield
Meridional flow profile measurements with SOHO/MDI and future requirements for instrumentation
We present meridional flow measurements of the Sun using a novel helioseismic approach to analyze SOHO/MDI data in order to push the current limits in both radial depth as well as time dependency. We will also put our observations and analysis into context with other techniques. And finally, we shall discuss requirements for future instrumentation for measuring the entire meridional flow profile from the solar surface down to the tachocline.

Sergey Moiseenko, Space Research Institute
Magnetorotational supernovae and magnetorotational instability formation
Magnetorotational(MR) mechanism of supernova explosion is discussed. Results of 2D simulations show, that MR mechanism leads to the supernova explosion with the explosion energy 0.5-0.6 10(51)erg. MR instability forms during our simulations.

Katalin Ilona Oláh, Konkoly Observatory
Multiple cycles in active stars
With K.G. Strassmeier, T. Granzer
We investigated continuous long-term photometric datasets of eleven active stars, plus sunspot numbers and 11cm radio data of the Sun, with Fourier- and time-frequency analysis. The data reflect the strength of the activity manifested in spots. All studied stars show multiple (2 to 4) cycles of different lengths using both methods, and in most cases the results confirm each other. The time-frequency analysis reveals, that in case of seven stars of the sample one or two of their cycles exhibit continuous changes (increase or decrease). For four stars (V711 Tau, IL Hya, HK Lac and the Sun) we find that the cycle length changes are strong, amounting to 10-50% during the observed time intervals. The rotational period - cycle length diagram, supplemented with new results from us and from the literature, confirms our previous relation: stars with shorter rotational periods generally show shorter cycles.

Orkun Özdarcan, Ege University Observatory
Photometric Period Analysis of V889 Herculis (Talk -> Poster)
In this study, photoelectric photometry of young active single star V889 Herculis (HD171488) is presented. Johnson V band data observed during 11 years were analyzed to investigate long term cyclic brightness variations, photometric period variations and evolution of activity related structures on star’s surface and differential rotation

Ana Palacios, GRAAL-Université Montpellier II
Rotation in the extended turbulent convective envelope of a red giant star
The first 3D non-linear hydrodynamical simulation of the inner convective envelope of a rotating low mass red giant star computed with the ASH code are presented.These simulations aim at constraining the redistribution of angular momentum in extended convective regions. The interactions between convection and rotation give rise to a large radial differential rotation and a meridional circulation possessing one cell per hemisphere, the flow being poleward in both hemisphere. The transport of angular momentum by meridional circulation appears to be outward in the radial direction and poleward in the latitudinal direction, the transport by Reynolds stresses acting in the opposite direction.This 3-D simulation will serve as a numerical experiment that will help deriving an average radial rotation law that will be useful for 1-D stellar evolution studies.

Valery Pipin, Institute Solar-Terrestrial Physics
The Omega x J effect in solar and stellar dynamos (Talk -> Poster)
With N. Seehafer
We present some results of investigations of the Omega x J effect in axisymmetric mean-field dynamos. This effect results from the joint action of the Coriolis force and the large-scale electric current associated with a nonuniform large-scale magnetic field on convection. It is equivalent to an anisotropic electrical conductivity and has been little investigated in the context of solar and stellar dynamos. For the solar dynamo, we explore a model containing this effect as well as the actions of cyclonic convection (alpha effect) and differential rotation (Omega effect). A kinematic model of a dynamo in a spherical shell is developed. The model takes into account the current knowledge of the distributions of the angular velocity and the intensity of the convection flows in the solar interior. We determine the relative strengths of the alpha and Omega x J effects such as to obtain a solar-type dynamo. Generally, the inclusion of the Omega x J effect increases the simulated period of the dynamo. Another effect is the concentration of the large-scale toroidal field towards the equator. The findings for the kinematic model are complemented by numerical results for a nonlinear evolution model. Furthermore, we give a first example of a delta^2 dynamo which is based solely on the joint induction effects of rotation and a large-scale current. This kind of dynamo may be relevant for fully convective stars. A simplified kinematic model of an axisymmetric dynamo in a rotating sphere is developed for this case.

Ansgar Reiners, Institute for Astrophysics / Univ. Göttingen
Differential Rotation in F-stars
Differential rotation in the Sun and other stars can be observed in migrating spots with latitude dependent angular velocity. Moreover, differential rotation affects the shape of the undistorted line profile and thus can be detected in the absence of spots, too. Because this method can measure the rotation law from a single profile, large samples can be investigated. I will review the potential of detecting differential rotation in line profiles and summarize differential rotation measurements we carried out in a survey of several hundred F-stars.

Ansgar Reiners, Institute for Astrophysics / Univ. Göttingen
Ultra-Cool and Extra-Vigorous: Rotation and activity in M- and L-dwarfs
The rotation-activity connection is a long known phenomenon that explains the rotational history of Sun-like stars and their weakening of magnetic activity with age. Magnetic activity in the Sun and other stars possessing a radiative core and a convective envelope is believed to be driven mainly by an interface dynamo situated at the tachocline. Towards lower temperatures, the tachocline moves inwards until the stars become fully convective at spectral types around mid-M. No interface dynamo can work in stars any cooler, but no break in activity is observed. Surveys carried out at VLT and Keck observatories have provided a wealth of new information on rotation, activity, and magnetic fields in ultracool objects. I will review the status of rotation and activity measurements at the end of the main sequence, and I give an overview about our knowledge on activity and rotational braking in ultracool stars and Brown Dwarfs.

Andreas Reisenegger, MPI f. Astrophys. / P. U. Católica de Chile
Magnetic field evolution in neutron stars
Some upper main sequence stars, white dwarfs, and neutron stars appear to have long-lived, large-scale, organized magnetic field configurations. Recent simulations by J. Braithwaite and collaborators support the existence of magnetohydrodynamic (MHD) equilibria that might account for these configurations, and which are nearly axisymmetric, involving poloidal and toroidal field components inside the stars. In ideal MHD theory, these equilibria appear to be stable, but they could in principle evolve through processes departing from ideality, causing the phenomenology of ``magnetars'', strongly magnetized neutron stars that exhibit occasional ``soft gamma-ray bursts'' and persistent, possibly thermal X-ray emission. Candidates for such non-ideal MHD effects are Hall drift, Urca processes, and ambipolar diffusion:\begin{itemize}\item Hall drift occurs because the currents supporting the magnetic fields require a relative motion of the positively charged particles, which carry most of the mass (and are fixed inthe solid crust of a neutron star), and the electrons, which transport the magnetic flux. Although its governing equation iseasy to write down, it is nonlinear, thus the generic outcome ofthis evolution is unknown.\item Urca processes transform neutrons into protons and electrons, or vice-versa. This is important because it allows bulk fluid motions to overcome the constraints imposed by the stable stratification due to the radially varying proton/neutron number density ratio.\item Ambipolar diffusion is a relative motion of all charged particles with respect to the neutrons, caused by the Lorentz force acting on the former, but not on the latter, and opposed by by mutual collisions. Eventually, pressure gradients in the charged particles will choke some kinds of motions and can be overcome only by Urca processes transforming charged particles into neutrons or vice-versa.\end{itemize}I will discuss how these processes affect axisymmetric, stable MHD equilibria, providing some insight into how magnetic field evolution in neutron stars may proceed. We find, among other things, that Hall drift is generally cancelled by bulk motions in the fluid core of the star, making it relevant only in the solid crust. Here, it may create current sheets where the crust may break, or at least resistive dissipation may become strong enough to substantially reduce the magnetic energy.

Matthias Rempel, HAO/NCAR
Non-kinematic flux-transport dynamos with variable meridional flow
A single counter clockwise flow cell is the assumption underlying most flux-transport models to date. On the other hand, global 3D simulations of the solar convection zone by Miesch et al. indicate that the meridional flow is strongly variable and shows at a given time a multi-cellular flow structure, with only the long term average reflecting a more regular flow field. We investigate the influence of such a highly time variable meridional flow on a flux-transport dynamo model. In our model the differential rotation and meridional flow are driven self-consistently through a parametrization of the Reynolds-stress (Lambda-effect) and also macroscopic Lorentz-force feedback is considered. We achieve the time variable flow by adding random fluctuations with a given correlation time and length scale to both components of the turbulent angular momentum flux. We find that a significant amount of random fluctuations can be tolerated before the dynamo loses its coherence, provided that the correlation time scale of the random component is significantly shorter than the cycle length.

Maria Victoria Rodriguez Ledesma, Max Planck Institute fuer Astronomie
Rotation of low mass stars in the Orion Nebula Cluster (Poster)
With R. Mundt, J. Eisloeffel, W. Herbst
We present preliminary results of a rotational period study of young low-mass stars and brown dwarfs in the Orion Nebula Cluster (ONC), based on photometric monitoring using the Wide Field Imager camera on the 2.2 meter telescope in La Silla, Chile (field size 34 x 33 arcmin). As in similar studies of this type the rotational brightness modulation by magnetic spots is used as an observational method. In addition to magnetically induced cool spots brightness modulation in young stars can also be caused by hot spots resulting from magnetically-channeled accretion flows. The latter spots can in principle generate much stronger brightness modulations than the former ones. About 3500 stars with I magnitudes between 13 and 21 mag have been monitored of which only a certain (still unknown) fraction will be ONC members. Time series data with a total of about 90 data points were obtained over 19 nights in December 2004 and the achieved photometric accuracy ranges from about 0.001 mag (for I = 13 mag) to 0.01 mag (for I = 19 mag). Power spectral analysis using both Scargle periodogram and the CLEAN algorithm was performed to search for evidence of periodic variability. False-alarm probabilities, using different techniques have been calculated. About 400 objects present detectable periodic light modulations, with most periods between 0.5 and 3 days. We will compare the obtained period distribution with those of higher-mass objects in the ONC and with low-mass objects in other star forming regions. A study of the dependence of the periodic brightness modulation on the magnitude (mass) of the object is under way. This should give insights on the magnetic spot properties as a function of mass in young stars.

Markus Roth, Max-Planck-Institut für Sonnensystemforschung
Helioseismic measurements of the meridional circulation
Helioseismology offers various techniques to measure large-scale flows in the solar interior. I will report on the helioseismic measurements of the meridional flow and its temporal evolution obtained by several measurement techniques.

Igor Savanov, Armagh Observatory
Evolution of starspots from the photometric light-curve inversions (Poster)
With K.G. Strassmeier
We present a novel technique of time-resolved light-curve inversions and apply it to the analysis of flip-flops and starspots evolution.

Rolf Schlichenmaier, Kiepenheuer-Institut fuer Sonnenphysik
Relation between photospheric magnetic field and chromospheric emission
With R. Rezaei, C. Beck, J. Bruls, W. Schmidt
We investigate the relationship between the photospheric magnetic field and the emission of the mid chromosphere of the Sun. We simultaneously observed the Stokes parameters of the photospheric iron line pair at 630.2 nm and the intensity profile of the chromospheric Ca II H line at 396.8 nm in a quiet Sun region at a heliocentric angle of 53°. Various line parameters have been deduced from the Ca II H line profile. The photospheric magnetic field vector has been reconstructed from an inversion of the measured Stokes profiles. After alignment of the Ca and Fe maps, a common mask has been created to define network and inter-network regions. We perform a statistical analysis of network and inter-network properties. The H-index is the integrated emission in a 0.1 nm band around the Ca core. We separate a non-magnetically, H_non, and a magnetically, H_mag, heated component from a non-heated component, H_co in the H-index.
The average network and inter-network H-indices are equal to 12 and 10 pm, respectively. The emission in the network is correlated with the magnetic flux density, approaching a value of H~10 pm for vanishing flux. The inter-network magnetic field is dominated by weak field strengths with values down to 200 G and has a mean absolute flux density of about 11 Mx cm^-2.
We find that a dominant fraction of the calcium emission caused by the heated atmosphere in the magnetic network has non-magnetic origin (H_mag~2 pm, H_non~3 pm). Considering the effect of straylight, the contribution from an atmosphere with no temperature rise to the H-index (H_co~6 pm) is about half of the observed H-index in the inter-network. The H-index in the inter-network is not correlated to any property of the photospheric magnetic field, suggesting that magnetic flux concentrations have a negligible role in the chromospheric heating in this region.

Manfred Schüssler, MPS
Are solar cycles predictable?
Attempts to predict future solar activity levels on various time scales have a long history - and not one that could be justifiably called a success story. The problem also has some relevance outside science in connection with the impact of what is nowadays called "space weather" on terrestrial and space-based technical systems. Recently, Dikpati & coworkers proposed a prediction method based upon a flux transport dynamo model combined with the assimilation of observed sunspot group areas. Their surprisingly precise postdiction of the amplitudes of the last 9 cycles (with a correlation coefficient of nearly 0.99) based on this model found widespread interest and, at the same time, stirred an ongoing (and not always pleasant) scientific debate. In this talk, I shall briefly review the subject of solar cycle prediction and try to elucidate the physics underlying the more succesful attempts: after all, our main aim is to learn something about the Sun. From these considerations, I shall give a tentative answer to the question in the title - an answer that will predictably dissatisfy most parties in the ongoing controversy.

Norbert Seehafer, Universität Potsdam
Force-free magnetic fields in the solar atmosphere
With M. Fuhrmann, G. Valori, B. Kliem
Reliable measurements of the solar magnetic field are restricted to the level of the photosphere. The situation here has not changed very much over the last half century. For about this time attempts have been made to calculate the field in the layers above the photosphere, i.e. in the chromosphere and in the corona, from the measured photospheric one. The procedure is known as magnetic field extrapolation. For typical plasma parameters in the superphotospheric parts of active regions, except for the times of explosive events, the magnetic field must be approximately force-free, i.e. electric currents aligned with the magnetic field. The practical application to solar active regions has been largely confined to constant-alpha or linear force-free fields, with a spatially constant ratio alpha between the electric current and the magnetic field. We review results obtained from extrapolations with constant-alpha force free fields, in particular on magnetic topologies favourable for flares and on magnetic and current helicities. Presently, different methods are being developed to calculate non-constant-alpha or nonlinear force-free fields from photospheric vector magnetograms. We discuss these methods and present examples of their application.

Selim O. Selam, Ankara Univ., Dept.of Astronomy and Space Sciences
Activity Induced Orbital Period Variations of Late-type Close Binaries (Poster)
A significant number of close binary systems that having at least one solar-type cool component star (i.e. RS CVn's, W UMa's, Algols or CV's) are show cyclic variations in their orbital period over the time-scales of several decades or more. These type of variations can be easily followed on the O-C diagrams constructed with their all observed times of eclipse minima and can be explained on the basis of two possible mechanisms, the magnetic activity cycle effect of the active component(s) and/or the light-time effect of a physically bound additional component(s) to the system. In this study the O-C analysis results of several late-type close binaries are presented in the context of magnetic activity cycle effect.

Jürgen Staude, Astrophysikalisches Institut Potsdam
Global vortical, Rossby-like modes with long periods in the solar interior
Retrograde waves with periods much larger than the rotation period become trapped in the solar radiative interior. The modelling considers compressible, nonadiabatic, Rossby-like modes (epsilon-mechanism and radiative losses are taken into account) for a very small latitudinal gradient of rotation, without an arbitrary choice of other free parameters. The modes with periods around 1-3, 18-30, and >1500 years are those with a maximum increment.

Matthias Steffen, Astrophysikalisches Institut Potsdam
Rotating star-in-a-box experiments
With B. Freytag
Using the radiation hydrodynamics code CO5BOLD in its 'star-in-a-box' setup, we have performed exploratory simulations of global convection in a rotating reference frame. The goal is to study the interaction of convection and rotation by direct numerical simulation. For these first experiments, we chose an idealized configuration (a scaled-down, fast rotating Sun) that has not yet a direct relation to real stars. We describe the setup and time evolution of this model, and discuss the particular problems we have encountered so far. Finally, we try to derive the resulting differential rotation pattern and meridional flow field by temporal and azimuthal averaging of the simulation data.

Michal Svanda, Astronomical Institute, Charles University
On the meridional flux transport in the photosphere of the Sun. (Poster)
With A.G. Kosovichev, J. Zhao
We measure the meridional flux transport displayed in the magnetic butterfly diagram sketching the large-scale evolution of the surface magnetic fields on the Sun. We have found that measured flux-transport remains more-or-less constant during the solar cycle. The impact for dynamo theories is discussed.

Maurizio Ternullo, INAF - Osservatorio Astrofisico di Catania
Looking inside the butterfly diagram
The evolution of the spot zone in cycles 20 through 23 has been studied on the basis of the data collected at the INAF - Osservatorio Astrofisico di Catania. In each semicycle (the northern and southern hemispheres have been treated separately) the daily spotted area undergoes pronounced oscillations, with five or six maxima per semicycle. Moreover, in each semicycle the equatorward drift of the spot zone geometrical "center-of-mass" (c.m.) results from the alternation of five or six prograde (namely, equatorward) segments, with other stationary or retrograde (poleward) segments. The time each semicycle spends in its stationary/retrograde phases is longer than ~ 30% of its total duration. The drift rate, computed on the basis of the prograde phases only, is almost twice the rate resulting from the extreme positions of the c.m. (at the beginning and at the end of the cycle): if there were no stationary/retrograde phases, the cycle duration would be half the actual one. The time intervals between homologous phases range from 1 to ~2 years, with an average value of ~1.6 years. These figures are compatible with those regarding the oscillations of the tachocline rotation rate. It seems reasonable that a cause-effect relationship links the tachocline rotation rate oscillation with both the pulsating photospheric activity and the variations of the spot zone drift rate.

Andrey Tlatov, Kislovodsk solar station
Duration of the extended solar cycles and amplitude of sunspot cycle (Talk -> Poster)
Duration of the extended solar cycles is taken into the consideration. The beginning of cycles is counted from the moment of polarity reversal of large-scale magnetic field in high latitudes, occurring in the sunspot cycle n till the minimum of the cycle n+2. The connection between cycle duration and its amplitude is established. Duration of the "latent" period of evolution of extended cycle between reversals and a minimum of the current sunspot cycle is entered. It is shown, that the latent period of cycles evolution is connected with the next sunspot cycle amplitude and can be used for the prognosis of a level and time of a sunspot maximum. The 24th activity cycle prognosis is done. Long-term behavior of extended cycle's lengths is considered.

Andrey Tlatov, Kislovodsk solar station of the Pulkovo observatory
22-years variations rotation of the Sun and solar activity cycles
The comparative analysis of long-term variations of rotation by results of data processing large-scale magnetic fields in H-alpha line, magnetographics observations and the corona observation in 5303A is executed. From analysis the observant data for the period more than 100 years are found out 22-years variations of solar rotation. Delay of rotation speed at low latitudes falls at an epoch close to a maximum of odd cycles of activity. Waves of a deviation of rotation speed drift from high latitudes to equator in time comparable with duration of a magnetic cycle. The possibility of generation of a solar magnetic cycle by interaction 22-years torsional fluctuations with slowly varying or relic magnetic field is discussed.

Steven Tobias, University of Leeds
Beta-Plane MHD turbulence in the solar tachocline
This talk discusses the role of a weak toroidal magnetic field in modifying the turbulent transport properties of stably stratified rotating turbulence in the tachocline. We construct a local two-dimensional model based on thebeta-plane approximation, which issolved numerically. In the absence of magnetic fields, the presence ofRossby waves and nonlinear interactions leads to the formation ofstrong mean zonal flows (as expected). However the addition of a weaktoroidal field suppresses the generation of mean flows. We calculate ascaling for the threshold between the formation and absence of meanows and argue that this has serious implications for angular momentumtransport in the lower tachocline.

Nathalie Toque, Saint Mary's University
Rapid differential rotation in massive stars
We use a 2D stellar evolution code [Deupree 1990] to simulate evolution on the main sequence of axi-symmetric stars for selected conservative rotation laws. The conservation of mass, momentum, energy and composition equations, and Poisson equation are all solved simultaneously with the Henvey method (a variant of the Newton-Raphson method) with the appropriate boundary conditions. We have calculated a number of ZAMS stellar models with uniform and differential rotation. We impose initial angular velocity distribution based on [Jackson 2005]: Omega(s) = Omega_0 / [1+(alpha s)^beta], where s is the distance from the axis of rotation and beta governs the differential rotation. We first introduce the correction of the total potential in order to take into account the differential rotation. We will show several ZAMS models with masses around 10 solar masses for various Omega_0 and beta values and alpha = 2. The independent variables are the fractional surface equatorial radius and the colatitude and we show that the appropriate dependant variables are constant on equipotential surfaces. The exception is the model surface, where the coupling of the effective temperature and the surface temperature through an imposed T-tau relation is inconsistent with the Von Zeipel formulation which requires the surface temperature to be constant while the effective temperature may vary significantly with the latitude. We use the results from these simulations and PHOENIX stellar atmospheres calculations to determine the observed effective temperature and luminosity as functions of the inclination between the observer and the rotation axis. We also compute pulsation periods for selected modes to determine if this provides clues about whether stars are differentially rotating. Deupree, R.G., ApJ (1990) 357, 175-187. Jackson, S., MacGregor, K.B. and Skumanich, A., ApJS (2005) 156(2), 245-264.

Ilkka Tuominen, Observatory, University of Helsinki
Kinematic frames and "active longitudes": does the Sun have a face (Poster)
With M.J. Korpi, J. Pelt and J.M. Brooke

Krisztián Vida, Eötvös University
Differential rotation and surface flow pattern on UZ Librae (Poster)
With Zs. Kövári, M. Svanda, K. Oláh, J. Bartus, E. Forgács-Dajka, K.G. Strassmeier
We re-investigate UZ Librae spectra obtained at KPNO in 1998 and 2000. From the 1998 data we compose 11 consecutive Doppler images using Ca I-6439 and Fe I-6393 Fe I-6411 lines. Applying the technique ACCORD (Average Cross-CORrelation of contiguous Doppler images, see Kövári et al. 2004), wfind anti-solar differential rotation with a shear of -0.03. The application of the LCT (Local Correlation Tracking) method (Svanda et al. 2007) for the same data confirms the anti-solar differential rotation and also suggests complex flow pattern on the stellar surface. For the cross-correlation of the two additional Doppler images in 2000 we also get anti-solar DR but with much weaker alpha of -0.004. Our findings agree with the result in Oláh et al. (2003) using 9 years of photometric data.

Christopher Watson, University of Sheffield
Indirect imaging of interacting binaries
Interacting binaries such as Cataclysmic Variables (CVs) contain some of the most rapidly rotating late-type stars known. With rotation periods as short as an hour, images of these systems should provide tests of stellar dynamo theories at ultra-fast rotation rates. Magnetic activity is also thought to play a key role in the evolution, behaviour and accretion dynamics of interacting binaries. I briefly review this subject area, before culminating in a series of images showing the late-type stars in AE Aqr, BV Cen, RU Peg and V426 Oph. While the sample is still small, the surface maps hint at a mechanism (probably tidal forces) that cause spots to erupt at preferred longitudes and around the mass transfer nozzle.

Nadezhda Zolotova, Saint-Petersburg State University
Enigma of the solar cycle 4
With D.I. Ponyavin
The problem of unusually long solar cycle 4 from 1784 to 1799, justbefore the Dalton Minimum, is considered. Why the length of the 4thcycle was exceptionally large or it was really composed of two shortcycles? Resolving this puzzle seems to be very important for dynamotheories trying to explain the solar long-term variations. We proposea possible scenario of the sunspot behavior during the solar cycle 4.The length and other peculiarities of the 4th solar cycle can resultfrom strong phase asynchrony between Northern and Southern hemisphericactivities. Analogies with the phase asynchronization observed in themodern epoch are presented and discussed.