How magnetic helicity ejection can speed up large scale dynamos
Abstract
There is mounting evidence that the ejection of magnetic helicity from the solar surface is of tremendous importance for the solar dynamo. Observations suggest that in the northern hemisphere the magnetic helicity flux is negative. We argue that this magnetic helicity flux is mostly due to small scale magnetic fields -- in contrast to the much more systematic large scale field of the 11 year cycle. We show, using idealized simulations of MHD turbulence as well as a simple two -scale model, that losses of small scale field can be responsible for enhancing the strength of the large scale field to observed levels. The losses of small scale field are also crucial for allowing the evolution of the large scale field to proceed on time scales shorter than the resistive time scale, that would otherwise be enforced by magnetic helicity conservation.
- Publication:
-
34th COSPAR Scientific Assembly
- Pub Date:
- 2002
- Bibcode:
- 2002cosp...34E3053B