Generation of a Large-scale Magnetic Field in a Convective Full-sphere Cross-helicity Dynamo

We study the effects of the cross-helicity in the full-sphere large-scale mean-field dynamo models of a 0.3 M star rotating with a period of 10 days. In exploring several dynamo scenarios that stem from magnetic field generation by the cross-helicity effect, we found that the cross-helicity provides...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2018-05, Vol.859 (1), p.18
Main Authors: Pipin, V. V., Yokoi, N.
Format: Article
Language:English
Subjects:
Astrophysics
Dipoles
dynamo
Dynamo theory
Helicity
Magnetic fields
Magnetic properties
Magnetism
Rotating bodies
Rotating generators
stars: activity
stars: low-mass
Stellar magnetic fields
Stellar rotation
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We study the effects of the cross-helicity in the full-sphere large-scale mean-field dynamo models of a 0.3 M star rotating with a period of 10 days. In exploring several dynamo scenarios that stem from magnetic field generation by the cross-helicity effect, we found that the cross-helicity provides the natural generation mechanisms for the large-scale scale axisymmetric and nonaxisymmetric magnetic field. Therefore, the rotating stars with convective envelopes can produce a large-scale magnetic field generated solely due to the turbulent cross-helicity effect (we call it γ2-dynamo). Using mean-field models we compare the properties of the large-scale magnetic field organization that stems from dynamo mechanisms based on the kinetic helicity (associated with the 2 dynamos) and cross-helicity. For the fully convective stars, both generation mechanisms can maintain large-scale dynamos even for the solid body rotation law inside the star. The nonaxisymmetric magnetic configurations become preferable when the cross-helicity and the -effect operate independently of each other. This corresponds to situations with purely γ2 or 2 dynamos. The combination of these scenarios, i.e., the γ2 2 dynamo, can generate preferably axisymmetric, dipole-like magnetic fields at strengths of several kGs. Thus, we found a new dynamo scenario that is able to generate an axisymmetric magnetic field even in the case of a solid body rotation of the star. We discuss the possible applications of our findings to stellar observations.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aabae6