2011MNRAS.412..107A

2011MNRAS.412..107A - Mon. Not. R. Astron. Soc., 412, 107-119 (2011/March-3)

Amplification and stability of magnetic fields and dynamo effect in young A stars.

This study is concerned with the early evolution of magnetic fields and differential rotation of intermediate-mass stars which may evolve into Ap stars. We report on simulations of the interplay of differential rotation and magnetic fields, the stability limits and non-linear evolution of such configurations, and the prospects of dynamo action from the unstable cases. The axisymmetric problem delivers a balance between field amplification and back-reaction of the magnetic field on the differential rotation. The non-axisymmetric case involves also the Tayler instability of the amplified toroidal fields. We consider limits for field amplification and apply these to young A stars.

Apart from its application to Ap stars, the instability is scrutinized for the fundamental possibility of a dynamo. We are not looking for a dynamo as an explanation for the Ap star phenomenon. The kinetic helicity is concentrated near the tangent cylinder of the inner sphere of the computational domain and is negative in the Northern hemisphere. This appears to be a ubiquitous effect not special to the Tayler instability. The latter is actually connected with a positive current helicity in the bulk of the spherical shell giving rise to a small, but non-vanishing α-effect in non-linear evolution of the instability.

Abstract Copyright: 2010 The Authors Monthly Notices of the Royal Astronomical Society2010 RAS

Journal keyword(s): MHD - stars: chemically peculiar - stars: magnetic field

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag U	Mag B	Mag V	Mag R	Mag I	Sp type	#ref 1850 - 2026	#notes
1	V* V901 Ori	Ro*	05 40 56.3704617744	-01 30 25.856677224	5.96	6.82	6.96			B2V	354	2

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`HD 37776`	`GEN# +1.00037776`	`ROT 910`	*`V V901 Ori`**
`AG-01 624`	`GSC 04767-01406`	`SAO 132446`	`VDB 51`
`ALS 8488`	`HIC 26742`	`SKY# 9266`	`WEB 5274`
`AP J05405637-0130257`	`HIP 26742`	`TD1 5138`	`WH 465`
`BD-01 1005`	`LS VI -01 3`	`TIC 11400909`	`YZ 91 1447`
`CEL 923`	`2MASS J05405637-0130257`	`TYC 4767-1406-1`	`[SC93b] 384`
`CSV 6381`	`PPM 175998`	`UBV 5793`	`Gaia DR2 3217413606922372992`
`GCRV 3521`	`Renson 10190`	`uvby98 100037776`	`Gaia DR3 3217413606922372992`

`HD 37776`	`AG-01 624`	`ALS 8488`	`AP J05405637-0130257`	`BD-01 1005`
`CEL 923`	`GSC 04767-01406`	`HIC 26742`	`HIP 26742`	`LS VI -01 3`
`2MASS J05405637-0130257`	`PPM 175998`	`SAO 132446`	`TD1 5138`	`TYC 4767-1406-1`
`uvby98 100037776`	*`V V901 Ori`**	`VDB 51`	`Gaia DR2 3217413606922372992`	`Gaia DR3 3217413606922372992`