Large scale dynamos with ambipolar diffusion nonlinearity
Abstract
It is shown that ambipolar diffusion as a useful model for nonlinearity leads to similar behaviour of large scale turbulent dynamos as full MHD. This is demonstrated using both direct simulations in a periodic box and a closure model for the magnetic correlation functions applicable to infinite space. Large scale fields develop via a nonlocal inverse cascade as described by the alpha -effect. However, magnetic helicity can only change on a resistive timescale, so the time it takes to organize the field into large scales increases with magnetic Reynolds number.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2000
- DOI:
- 10.48550/arXiv.astro-ph/0007450
- arXiv:
- arXiv:astro-ph/0007450
- Bibcode:
- 2000A&A...361L..33B
- Keywords:
-
- HYDRODYNAMICS;
- MAGNETIC FIELDS;
- MAGNETOHYDRODYNAMICS (MHD);
- TURBULENCE;
- STARS: MAGNETIC FIELDS;
- GALAXIES: MAGNETIC FIELDS;
- Astrophysics
- E-Print:
- 4 pages, 5 figures