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The Solar Course, the Chemic Force, and the Speeding Change of Water

→ Europe/Stockholm
Nordita lecture room (NORDITA)

Nordita lecture room

NORDITA

Roslagstullsbacken 23
Dhrubaditya Mitra (Asssitant Professor)
Description

→ link to photos and conference picture (taken by Chi-kwan Chan, Nordita)

→ link to video server with all recordings.

A multidisciplinary program to celebrate the 70th birthday of Uriel Frisch. The principal scientific topics are going to be turbulence, nonlinear dynamics, statistical mechanics, atmospheric and biological applications of nonlinear physics.
A tentative list of themes includes 

  (1) Fluid turbulence
  (2) Turbulent dynamo
  (3) Optimal transport and applications
  (4) Biologically inspired problems
Scientific organizing committee: 
  •  Erik Aurell

  •  Jeremie Bec

  •  M-E Brachet

  •  Axel Brandenburg

  •  Takeshi Matsumoto

  •  Annick Pouquet

  •  Andrei Sobolebski

  •  Zhen-Su She

  •  Dario Vincenzi

  •  Massimo Vergassola
    • Local organizing committee: 
  •  Erik Aurell

  •  Axel Brandenburg

  •  Dhrubaditya Mitra

    • The meeting is sponsored jointly by Nordita, Swedish Research Council, CNRS, and the Astrophysical Dynamo ERC Project

    • Monday 17 October
      • 09:30 → 10:00
        Turbulent convection in three, two and one dimensions. 30m
        Speaker: G Boffetta
        Slides
        video
      • 10:00 → 10:30
        Energy and enstrophy cascades in large scale atmospheric turbulence 30m
        Speaker: E. Lindborg
        Slides
        video
      • 11:00 → 11:30
        Asymptotic stability of heteroclinic cycles 30m
        Dynamical systems, equivariant under the action of a non-trivial symmetry group, can possess structurally stable heteroclinic cycles. We consider stability properties of a class of structurally stable heteroclinic cycles in $\R^n$, which we call heteroclinic cycles of type Z. It is well-known that a heteroclinic cycle, that is not asymptotically stable, can attract nevertheless a positive measure set from its neighbourhood. We call such cycles fragmentarily asymptotically stable. Necessary and sufficient conditions for fragmentary asymptotic stability are expressed in terms of eigenvalues and eigenvectors of transition matrices. If all transverse eigenvalues of linearisations near steady states that are involved in the cycle are negative, then the condition for asymptotic stability is that the transition matrices have an eigenvalue larger than one in absolute value. Finally, we discuss bifurcations occurring when the conditions for asymptotic stability or for fragmentary asymptotic stability are broken
        Speaker: O. Podvigina
        Slides
        video
      • 11:30 → 12:00
        Computing non-equilibrium stationary states by message-passing? 30m
        Speaker: E. Aurell
        video
      • 12:00 → 12:30
        Rotating Turbulence and return to isotropy. 30m
        Speaker: A. Pouquet
        Slides
        video
      • 14:30 → 15:15
        Dynamics of the glassy state of matter 45m
        Speaker: I. Procaccia
        video
      • 15:45 → 16:15
        Pirouette effect in turbulence 30m
        Speaker: A. Pumir
        video
      • 16:15 → 16:45
        Scaling and Intermittency in fluctuating Alpha-Shear dynamos 30m
        We consider mean-field dynamo models with fluctuating \alpha effect, both with and without shear. The \alpha effect is chosen to be Gaussian white noise with zero mean and given covariance. We show analytically that the mean magnetic field does not grow, but, in an infinitely large domain, the mean-squared magnetic field shows exponential growth of the fastest growing mode at a rate proportional to the shear rate, which agrees with earlier numerical results of Yousef et al (2008) and recent analytical treatment by Heinemann et al (2011) who use a method different from ours. In the absence of shear, an incoherent \alpha^2 dynamo may also be possible. We further show by explicit calculation of the growth rate of third and fourth order moments of the magnetic field that the probability density function of the mean magnetic field generated by this dynamo is non-Gaussian.
        Speaker: D. Mitra (NORDITA)
        Slides
        video
    • Tuesday 18 October
      • 09:00 → 09:45
        Optimization in astrophysics 45m
        Speaker: R. Mohayee (AIP, Paris)
      • 09:45 → 10:15
        Negative effective magnetic pressure instability 30m
        We present the first demonstration of the negative effective magnetic pressure instability in direct numerical simulations of stably stratified, externally forced, isothermal hydromagnetic turbulence in the regime of large plasma beta. By the action of this instability, an initially uniform horizontal magnetic field forms flux concentrations whose scale is large compared to the turbulent scale. We further show that the magnetic energy of these large-scale structures is only weakly dependent on the magnetic Reynolds number, provided its value is large enough for the instability to be excited. Our results support earlier mean-field calculations and analytic work which identified this instability. Applications to the formation of active regions in the Sun are discussed. [Astrophys. J. Lett. 740, L50 (2011) ]
        Speaker: A. Brandenburg
        Slides
      • 11:00 → 11:30
        Nelkin scaling for ¨burgulence¨ 30m
        Speaker: S. Chakraborty (NBI, Copenhagen)
        Slides
      • 11:30 → 12:00
        Relaxation of Galerkin-Truncated Gyrokinetic, and back to Magenticfluids 30m
        The gyrokinetic absolute equilibrium will be reviewed. Some numerical results of gyrokinetic simulations will be presented. Two-fluid magneticfluid absolute equilibrium is used to investigate two-fluid effects, effects of various helicities et al. This talk try to bring some new insights into the kinetic and two-fluid effects in magnetized plasma turbulence in fusion device, space and astrophysics.
        Speaker: J-Z Zhu
        Slides
      • 12:00 → 12:30
        Condensates in two dimensional turbulence 30m
        We derive and numerically confirm that the saturation of energy condensation in two-dimensional turbulence is governed by the balance between forcing and small-scale dissipation. The time scale of saturation is inversely proportional to the viscosity but the saturation energy level is determined by both viscosity and the forcing scale. It is shown that, because the energy dissipation is proportional to the enstrophy, which itself is a conserved quantity in the ideal case, it is necessary to resolve the enstrophy spectrum to achieve numerical consistency. We also find that the movement of the condensate vortices can be described as Brownian motion of an inertial particle. [arXiv:1109.6937v1]
        Speaker: C-K Chan
        Slides
      • 14:30 → 15:30
        On the Evolution of Texts: An Introduction to Stemmatology 1h
        Speaker: T Roos
        Slides
      • 15:30 → 16:30
        Nothing new under the burning sun? Climate and verbs in North-West Semitic 1h
        Speaker: O. Wikander
    • Wednesday 19 October
      • 09:00 → 09:45
        Time Scales, Persistence, and Dynamic Multiscaling in Turbulence 45m
        Speaker: R. Pandit (IISc, Bangalore)
        Slides
      • 09:45 → 10:15
        Orientation of non-symmetric particles in axisymmetric random flows 30m
        Speaker: D. Vincenzi
        Slides
      • 10:45 → 11:15
        Navier-Stokes in hyperbolic plane 30m
        Speaker: ENS, Lyon Gawedzki
        Slides
      • 11:15 → 11:45
        Axial dipolar dynamo action in Taylor-Green vortex 30m
        Speaker: M-E Brachet
        Slides
      • 11:45 → 12:15
        Role of polymers in the mixing of Rayleigh-Taylor turbulence 30m
        The role of polymer additives on Rayleigh-Taylor turbulence is investigated by means of direct numerical simulations (DNS) of Oldroyd-B viscoelastic model. The dynamics of polymer elongations follows adiabatically the self-similar evolution of the turbulent mixing layer and shows the appearance of a strong feedback on the flow which originates a cut off for polymer elongations. The viscoelastic effects on the mixing properties of the flow are twofold. Mixing is appreciably enhanced at large scales (the mixing layer growth-rate is larger than that of the purely Newtonian case) and depleted at small scales (thermal plumes are more coherent with respect to the Newtonian case). The observed speed up of the thermal plumes, together with an increase of the correlations between temperature field and vertical velocity, contributes to a significant enhancement of heat transport. Our findings are consistent with a scenario of drag reduction induced by polymers.
        Speaker: A Mazzino
        Slides
      • 14:30 → 15:00
        Life at high Reynolds number 30m
        Speaker: M Jensen
      • 15:00 → 15:30
        A Lie-group mean-field theory for turbulent channel and pipe flow 30m
        Speaker: Xi Chen
        Slides
      • 16:00 → 17:00
        Round table discussions 1h
    • Thursday 20 October
      • 09:30 → 10:15
        Structures versus statistics in turbulence, resolution of old quarrel 45m
        Speaker: G. Falkovich
      • 10:45 → 11:30
        Turbulence in non-integer dimensions by fractal Fourier decimation 45m
        Speaker: U. Frisch
        Slides
      • 11:30 → 12:00
        The tyger phenomenon for the Galerkin truncated Burgers equation. 30m
        Speaker: S.S. Ray (Obs Nice)
        Slides
      • 12:00 → 12:30
        On form and growth 30m
        Speaker: J Wettlaufer (NORDITA and Yale)
      • 14:30 → 14:50
        Inverse energy cascade in 3d isotropic and homogeneous turbulence 20m
        Speaker: L Biferale
        Slides
    • Friday 21 October
      • 09:30 → 10:15
        Population dynamics in compressible flows 45m
        Speaker: R. Benzi
        Slides
      • 10:45 → 11:15
        Lagrangian/Eulerian estimate of turbulent breakup of small particles 30m
        Speaker: A. Lanotte
        Slides
      • 11:15 → 11:45
        The size of the region of analyticity of solutions to the two-dimensional Euler equation 30m
        Speaker: V. Zheligovsky
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