On the emergence of toroidal flux tubes: general dynamics and comparisons with the cylinder model

Abstract

In this paper we study the dynamics of toroidal flux tubes emerging from the solar interior, through the photosphere and into the corona. Many previous theoretical studies of flux emergence use a twisted cylindrical tube in the solar interior as the initial condition. Important insights can be gained from this model, however, it does have shortcomings. The axis of the tube never fully emerges as dense plasma becomes trapped in magnetic dips and restrains its ascent. Also, since the entire tube is buoyant, the main photospheric footpoints (sunspots) continually drift apart. These problems make it difficult to produce a convincing sunspot pair. We aim to address these problems by considering a different initial condition, namely a toroidal flux tube. We perform numerical experiments and solve the 3D MHD equations. The dynamics are investigated through a range of initial field strengths and twists. The experiments demonstrate that the emergence of toroidal flux tubes is highly dynamic and exhibits a rich variety of behaviour. In answer to the aims, however, if the initial field strength is strong enough, the axis of the tube can fully emerge. Also, the sunspot pair does not continually drift apart. Instead, its maximum separation is the diameter of the original toroidal tube.

Accepted by A&A: 09 September 2009

References in corpus (4)

• Magnetic flux emergence in granular convection: Radiative MHD simulations and observational signatures
• Eruption of magnetic flux ropes during flux emergence
• MHD simulations of penumbra fine structure
• 3-D non-linear evolution of a magnetic flux tube in a spherical shell: the isentropic case

Cited by in corpus (12)

• Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections
• Simulations of Emerging Magnetic Flux. II: The formation of Unstable Coronal Flux Ropes and the Initiation of CMEs
• A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona
• The magnetic structure of surges in small-scale emerging flux regions
• Solar Magnetic Carpet II: Coronal Interactions of Small-Scale Magnetic Fields
• Interpreting magnetic helicity flux in solar flux emergence
• Successful and Failed Flux Tube Emergence in the Solar Interior
• The Rise and Emergence of Untwisted Toroidal Flux Ropes on the Sun
• Formation and Eruption of a Mini-sigmoid Originating in Coronal Hole
• Solar Interior
• Least-Squares Fitting Methods for Estimating the Winding Rate in Twisted Magnetic-Flux Tubes
• A comparative study of solar flux emergence and eruptivity in simulations of horizontal versus toroidal magnetic fields