Catastrophic alpha quenching alleviated by helicity flux and shear
| dc.creator | Brandenburg, Axel | |
| dc.creator | Sandin, Christer | |
| dc.date | 2004-01-14 | |
| dc.date | 2004-07-29 | |
| dc.date.accessioned | 2026-07-07T02:11:52Z | |
| dc.date.available | 2026-07-07T02:11:52Z | |
| dc.description | A new simulation set-up is proposed for studying mean field dynamo action. The model combines the computational advantages of local cartesian geometry with the ability to include a shear profile that resembles the sun's differential rotation at low latitudes. It is shown that in a two-dimensional mean field model this geometry produces cyclic solutions with dynamo waves traveling away from the equator -- as expected for a positive alpha effect in the northern hemisphere. In three dimensions with turbulence driven by a helical forcing function, an alpha effect is self-consistently generated in the presence of a finite imposed toroidal magnetic field. The results suggest that, due to a finite flux of current helicity out of the domain, alpha quenching appears to be non-catastrophic -- at least for intermediate values of the magnetic Reynolds number. For larger values of the magnetic Reynolds number, however, there is evidence for a reversal of the trend and that $α$ may decrease with increasing magnetic Reynolds number. Control experiments with closed boundaries confirm that in the absence of a current helicity flux, but with shear as before, alpha quenching is always catastrophic and alpha decreases inversely proportional to the magnetic Reynolds number. For solar parameters, our results suggest a current helicity flux of about 0.001 G^2/s. This corresponds to a magnetic helicity flux, integrated over the northern hemisphere and over the 11 year solar cycle, of about 10^{46}Mx^2. | |
| dc.description | 9 pages, 10 figures, A&A (in press) | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0401267 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0401267 | |
| dc.identifier | Astron.Astrophys. 427 (2004) 13-21 | |
| dc.identifier | doi:10.1051/0004-6361:20047086 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/7257 | |
| dc.subject | Astrophysics | |
| dc.title | Catastrophic alpha quenching alleviated by helicity flux and shear | |
| dc.type | text |