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Self-organized magnetic structures in computational astrophysics

Self-organized magnetic structures in computational astrophysics. Axel Brandenburg (Nordita/Stockholm). Kemel+12. K äpylä +12. Ilonidis+11. Warnecke+11. Brandenburg+13. Today. B-class flares?. Oct2003. Flights rerouted. Rerouted. 6 March. 7 March. 8 March.

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Self-organized magnetic structures in computational astrophysics

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  1. Self-organized magnetic structures in computational astrophysics Axel Brandenburg (Nordita/Stockholm) Kemel+12 Käpylä+12 Ilonidis+11 Warnecke+11 Brandenburg+13

  2. Today

  3. B-class flares?

  4. Oct2003

  5. Flights rerouted

  6. Rerouted

  7. 6 March

  8. 7 March

  9. 8 March

  10. Magnetic fields from the Sun • Motions from • Convection instability • Magnetorotational inst. • Supernova forcing • Dynamo instability • Stretch-twist-fold • Turbulent dynamo

  11. White light Tips of icebergs: Magnetic flux concentrations in magnetogram!

  12. Parker’s (1955) dynamo wave New loop Differential rotation (faster inside) Cyclonic convection; Buoyant flux tubes Equatorward migration  a-effect

  13. Doppler imaging: distant stars

  14. II Peg: rapidly rotating binary Saar & Brandenburg (1999) RS CVn type CanumVenaticorum Kochukhov, Mantere, et al (2013)

  15. Brun, Brown, Browning, Miesch, Toomre

  16. Ghizaru, Charbonneau, Racine, … • Cycle now common! • Activity from bottom of CZ • but at high latitudes

  17. Dynamo wave from simulations Kapyla et al (2012)

  18. Dynamo is one example of self-organization

  19. Alternative sunspot origins Kosovichev et al. (2000) Theories for shallow spots: (i) Collapse by suppression of turbulent heat flux (ii) Negative pressure effects from <uiuj> vs BiBj

  20. Negative effective magnetic pressure instability • Gas+turb. press equil. • B increases • Turb. press. Decreases • Net effect?

  21. Self-assembly of a magnetic spot • Minimalistic model • 2 ingredients: • Stratification & turbulence • Extensions • Coupled to dynamo • Compete with rotation • Radiation/ionization

  22. Mean-field models: different scale separation Varying turbulent diffusivity

  23. Bi-polar regions, found by accident Warnecke et al. (2013, submitted)

  24. Pencilcode • Started in Sept. 2001 with Wolfgang Dobler • High order (6th order in space, 3rd order in time) • Cache & memory efficient • MPI, can run PacxMPI (across countries!) • Maintained/developed by ~80 people (SVN) • Automatic validation (over night or any time) • 0.0013 ms/pt/step at 10243 , 2048 procs • http://pencil-code.googlecode.com • Isotropic turbulence • MHD, passive scl, CR • Stratified layers • Convection, radiation • Shearing box • MRI, dust, interstellar • Self-gravity • Sphere embedded in box • Fully convective stars • geodynamo • Other applications • Chemistry, combustion • Spherical coordinates

  25. Increase of revision number User meetings: 2005 Copenhagen 2006 Copenhagen 2007 Stockholm 2008 Leiden 2009 Heidelberg 2010 New York 2011 Toulouse 2012 Helsinki 2013 Lund 2014 Gottingen

  26. Pencil h-index Red line gives the diagonal to see the crossing

  27. Automatic validation tests

  28. Increase in # of auto tests

  29. Online data reduction and visualization non-helically forced turbulence

  30. Conclusions • Turbulence can possess surprising effects • Large scale dynamos • Magnetic flux concentrations • Importance for space weather • Run-time data evaluation, etc

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