Helicity and dynamo action in magnetized stellar radiation zones

Details Helicity and dynamo action in magnetized stellar radiation zones Helicity and dynamo action in magnetized stellar radiation zones

2011-07-13

arxiv.org/abs/1107.2548v1

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

11 pages, 8 figures, submitted to MNRAS

Scientific paper

Helicity and \alpha effect driven by the nonaxisymmetric Tayler instability of toroidal magnetic fields in stellar radiation zones are computed. In the linear approximation a purely toroidal field always excites pairs of modes with identical growth rates but with opposite helicity so that the net helicity vanishes. If the magnetic background field has a helical structure by an extra (weak) poloidal component then one of the modes dominates producing a net kinetic helicity anticorrelated to the current helicity of the background field. The mean electromotive force is computed with the result that the \alpha effect by the most rapidly growing mode has the same sign as the current helicity of the background field. The \alpha effect is found as too small to drive an \alpha^{2} dynamo but the excitation conditions for an \alpha\Omega dynamo can be fulfilled for weak poloidal fields. Moreover, if the dynamo produces its own \alpha effect by the magnetic instability then problems with its sign do not arise. For all cases, however, the \alpha effect shows an extremely strong concentration to the poles so that a possible \alpha\Omega dynamo might only work at the polar regions. Hence, the results of our linear theory lead to a new topological problem for the existence of large-scale dynamos in stellar radiation zones on the basis of the current-driven instability of toroidal fields.

Affiliated with

Also associated with

No associations

Rating

Helicity and dynamo action in magnetized stellar radiation zones does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Helicity and dynamo action in magnetized stellar radiation zones, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Helicity and dynamo action in magnetized stellar radiation zones will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-165841