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Alexander V. Getling

Cellular Compressible Magnetoconvection: A Mechanism for Magnetic-Field Amplification and Structuring. Alexander V. Getling Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia Wolfgang Dobler Kiepenheuer-Institut f ü r Sonnenphysik Freiburg, Germany.

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Alexander V. Getling

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  1. Cellular Compressible Magnetoconvection:A Mechanism for Magnetic-Field Amplification and Structuring Alexander V. Getling Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia Wolfgang Dobler Kiepenheuer-Institut für Sonnenphysik Freiburg, Germany

  2. Issues traditionally addressed (M. R. E. Proctor, N. O. Weiss, Å. Nordlund, R. Stein, F. Cattaneo, etc.): • Spatial separation of flow and magnetic flux • Oscillations and waves accompanying compressible magnetoconvection • “Realistic” description of magnetic flux tubes under nearly solar conditions

  3. Our alternative: The outer scale of the process ~ the size of a convection cell Main subject: the fine structure of the magnetic field within the cell → We study the role of cellular convection in amplification and structuring of magnetic fields

  4. Kinematic model(toroidal eddy) B. A. Tverskoy, Geomagn. Aeron. 6(1), 11–18, 1966

  5. Toroidal eddy

  6. Magnetic-field amplificationin a kinematic model

  7. The very topology of the cell produces bipolar configurations of amplified magnetic field

  8. Geometry of the problem

  9. Simulations in the Boussinesqapproximation: • A. V. Getling,Astron. Rep.45(7), 569–576, 2001. • A. V. Getling, I. L. Ovchinnikov, in Solar Variability: From Core to Outer Frontiers (ESA SP-506, 2002), p. 819–822.

  10. Velocity field(contours of vzin plane z/h = 0.5) Left: initial; middle: late for a large k0; right: latefor k0 = kc

  11. Pencil Code (6th order in space; 3rd order in time): A. Brandenburg, W. Dobler 2001 http://www.nordita.dk/data/ brandenb/pencil-code

  12. Physical parameters of the problem

  13. Parameter range explored

  14. Sample solutions

  15. Variation of magnetic field (initial magnetic field is horizontal)

  16. Structure of solutionin planes z/h = 0.07 (b)and 0.5 (a, c) (initial magnetic field is horizontal)

  17. Basic structural featureof amplified magnetic field: Bipolar configuration superposed with finer details

  18. Additional (previously known) effects • Sweep of vertical magnetic flux to cell boundaries • Concentration of horizontal magnetic flux near the lower boundary of the layer (“topological pumping”; see E. M. Drobyshevski, V. S. Yuferev, J. Fluid. Mech.65, 33–44, 1974)

  19. Variation of magnetic field (initial magnetic field is inclined)

  20. Structure of solutionin planes z/h = 0.07 (b)and 0.5 (a, c) (initial magnetic field is inclined)

  21. The case of an inclined initial magnetic field: Superposition of a bipolar and a unipolar configuration mixed in a proportion that depends on the inclination of the initial field

  22. Thank you for your attention

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