The Generation of Magnetic Fields in Astrophysical Bodies. III. Turbulent Diffusion of Fields and Efficient Dynamos

1971 ◽  
Vol 163 ◽  
pp. 279 ◽  
Author(s):  
E. N. Parker
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion

scholarly journals The role of magnetic fields for planetary formation

2008 ◽  
Vol 4 (S259) ◽  
pp. 249-258 ◽  
Author(s):  
Anders Johansen
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion ◽  
Planet Formation ◽  
High Pressures ◽  
Mixing Time ◽  
Zonal Flow ◽  
Coherence Time ◽  
Maxwell Stress ◽  
Turbulent Diffusion Coefficient

AbstractThe role of magnetic fields for the formation of planets is reviewed. Protoplanetary disc turbulence driven by the magnetorotational instability has a huge influence on the early stages of planet formation. Small dust grains are transported both vertically and radially in the disc by turbulent diffusion, counteracting sedimentation to the mid-plane and transporting crystalline material from the hot inner disc to the outer parts. The conclusion from recent efforts to measure the turbulent diffusion coefficient of magnetorotational turbulence is that turbulent diffusion of small particles is much stronger than naively thought. Larger particles – pebbles, rocks and boulders – get trapped in long-lived high pressure regions that arise spontaneously at large scales in the turbulent flow. These gas high pressures, in geostrophic balance with a sub-Keplerian/super-Keplerian zonal flow envelope, are excited by radial fluctuations in the Maxwell stress. The coherence time of the Maxwell stress is only a few orbits, where as the correlation time of the pressure bumps is comparable to the turbulent mixing time-scale, many tens or orbits on scales much greater than one scale height. The particle overdensities contract under the combined gravity of all the particles and condense into gravitationally bound clusters of rocks and boulders. These planetesimals have masses comparable to the dwarf planet Ceres. I conclude with thoughts on future priorities in the field of planet formation in turbulent discs.

Turbulent diffusion of magnetic fields

1978 ◽  
Vol 225 ◽  
pp. 1050 ◽  
Author(s):  
E. Knobloch
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion

scholarly journals On Cross-Phase and the Quenching of the Turbulent Diffusion of Magnetic Fields in Two Dimensions

2008 ◽  
Vol 678 (2) ◽  
pp. L137-L140 ◽  
Author(s):  
Shane R. Keating ◽  
L. J. Silvers ◽  
P. H. Diamond
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion ◽  
Two Dimensions

scholarly journals Turbulent Diffusion of Magnetic Fields in Weakly Ionized Gas

2002 ◽  
Vol 578 (2) ◽  
pp. L113-L116 ◽  
Author(s):  
Eun-jin Kim ◽  
P. H. Diamond
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion ◽  
Ionized Gas ◽  
Weakly Ionized

scholarly journals Turbulent diffusion with rotation or magnetic fields

2009 ◽  
Vol 395 (3) ◽  
pp. 1599-1606 ◽  
Author(s):  
Axel Brandenburg ◽  
Andreas Svedin ◽  
Geoffrey M. Vasil
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion

scholarly journals Vorticity from irrotationally forced flow

2010 ◽  
Vol 6 (S271) ◽  
pp. 375-376
Author(s):  
Fabio Del Sordo ◽  
Axel Brandenburg
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Turbulent Diffusion ◽  
Forced Flow ◽  
First Approximation ◽  
Supernova Explosions ◽  
Vorticity Generation

AbstractIn the interstellar medium the turbulence is believed to be forced mostly through supernova explosions. In a first approximation these flows can be written as a gradient of a potential being thus devoid of vorticity. There are several mechanisms that could lead to vorticity generation, like viscosity and baroclinic terms, rotation, shear and magnetic fields, but it is not clear how effective they are, neither is it clear whether the vorticity is essential in determining the turbulent diffusion acting in the ISM. Here we present a study of the role of rotation, shear and baroclinicity in the generation of vorticity in the ISM.

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