self-organized magnetic structures in computational astrophysics axel brandenburg...
DESCRIPTION
B-class flares? 3TRANSCRIPT
Self-organized magnetic structures Self-organized magnetic structures in computational astrophysicsin computational astrophysics
Axel Brandenburg (Nordita/Stockholm)
Kemel+12Kemel+12 Ilonidis+11Ilonidis+11 Brandenburg+13Brandenburg+13Warnecke+11Warnecke+11KKäpylääpylä+12+12
Today
2
B-class flares?
3
Oct2003
4
Flights rerouted
5
Rerouted
6
7
6 March
8
7 March
9
8 March
10
11
Magnetic fields from the SunMagnetic fields from the Suna) Motions from
i. Convection instabilityii. Magnetorotational inst.iii. Supernova forcing
b) Dynamo instabilityi. Stretch-twist-foldii. Turbulent dynamo
White light
12
Tips of icebergs:Magnetic flux concentrations in magnetogram!
13
ParkerParker’’s (1955) dynamo waves (1955) dynamo wave
Differential rotation(faster inside) Cyclonic convection;
Buoyant flux tubesEquatorward
migration
New loop
-effect
Doppler imaging: distant stars
14
II Peg: rapidly rotating binary
15
RS CVn type Canum Venaticorum
Kochukhov, M
antere, et al (2013)Saar &
Brandenburg (1999)
Brun, Brown, Browning, Miesch, ToomreBrun, Brown, Browning, Miesch, Toomre
16
17
• Cycle now common!
• Activity from bottom of CZ
• but at high latitudes
Ghizaru, Ghizaru, Charbonneau, Charbonneau,
Racine, …Racine, …
18
Dynamo wave from simulations Kapyla et al (2012)
19
Dynamo is one example of self-organizationDynamo is one example of self-organization
20
Alternative sunspot originsAlternative sunspot origins
Theories for shallow spots:Theories for shallow spots:
(i) Collapse by suppression(i) Collapse by suppressionof turbulent heat fluxof turbulent heat flux
(ii) Negative pressure effects(ii) Negative pressure effectsfrom <from <uuiiuujj> vs > vs BBiiBBjj
Kosovichev et al. (2000)
Kosovichev et al. (2000)
21
Negative effective magnetic pressure instability
• Gas+turb. press equil.
• B increases• Turb. press.
Decreases• Net effect?
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
23
Varying turbulent diffusivity
Bi-polar regions, found by accident
24
Warnecke et al. (2013, subm
itted)
PencilPencilcodecode
• 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 s/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
26
Increase of revision number Increase of revision number
User meetings:User meetings:2005 Copenhagen2006 Copenhagen2007 Stockholm2008 Leiden2009 Heidelberg2010 New York2011 Toulouse2012 Helsinki2013 Lund2014 Gottingen
Pencil h-index
27
Red line givesthe diagonal to see the crossing
28
Automatic validation testsAutomatic validation tests
29
Increase in # of auto testsIncrease in # of auto tests
30
Online data reduction and visualizationOnline data reduction and visualization
non-helically forced turbulence
Conclusions• Turbulence can possess surprising effects
– Large scale dynamos– Magnetic flux concentrations
• Importance for space weather• Run-time data evaluation, etc
31