Solar Dynamo and Toroidal Field Instabilities

Abstract

The possibility of non-axisimmetric (kink) instabilities of a toroidal field seated in the tachocline is much discussed in the literature. In this work, the basic properties of kink and quasi-interchange instabilities, produced by mixed toroidal and poloidal configuration, will be briefly reviewed. In particular it will be shown that the unstable modes are strongly localized near the Equator and not near the Poles as often claimed in the literature. Based on the results of recent numerical simulations, it is argued that a non-zero helicity can already be produced at a non-linear level. A mean-field solar dynamo is then constructed with a positive $\alpha$-effect in the overshoot layer localized near the Equator and a meridional circulation with a deep return flow. Finally, the possibility that the solar cycle is driven by a $\alpha \Omega$ dynamo generated by the negative subsurface shear in the supergranulation layer will also be discussed.

to appear in Solar Physics

References in corpus (11)

• The case for a distributed solar dynamo shaped by near-surface shear
• On magnetic instabilities and dynamo action in stellar radiation zones
• Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
• Stability of Toroidal Magnetic Fields in Rotating Stellar Radiation Zones
• Stability of magnetic configurations containing the toroidal and axial fields
• Non-axisymmetric instability of axisymmetric magnetic fields
• Mean-field solar dynamo models with strong meridional flow at the bottom of the convection zone
• Breakdown of chiral symmetry during saturation of the Tayler instability
• Helicity and dynamo action in magnetized stellar radiation zones
• Stability of the toroidal magnetic field in stellar radiation zones
• Resonance instability of axially-symmetric magnetostatic equilibria

Cited by in corpus (8)

• On the role of tachoclines in solar and stellar dynamos
• What sets the magnetic field strength and cycle period in solar-type stars?
• Asteroseismic stellar activity relations
• Magnetic activity, differential rotation and dynamo action in the pulsating F9IV star KIC 5955122
• Global simulations of Tayler instability in stellar interiors: a long-time multi-stage evolution of the magnetic field
• Acoustic oscillations and dynamo action in the G8 sub-giant EK Eri
• On the possibility of helicity oscillations in the saturation of the Tayler instability
• Global simulations of stellar dynamos