2002/11/27 by Arnab Rai Choudhuri · 77 citations
Engineering · Physics and Astronomy · #Convection #Convection zone #Dynamo #Fluid dynamics and aerodynamics studies #Flux (metallurgy) #Flux tube #Magnetic field #Magnetic flux #Scientific Research and Discoveries #Solar and Space Plasma Dynamics #Solar dynamo #Tachocline #astro-ph
paper · pdf · doi:10.1023/a:1024874816178
published in Solar Physics 215(1), 31-55 (Springer Science+Business Media) · 24 pages plain latex, 4 figures
arxiv created 2002/11/27 · openalex publication_date 2003/07/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Mean field dynamo theory deals with various mean quantities and does not directly throw any light on the question of existence of flux tubes. We can, however, draw important conclusions about flux tubes in the interior of the Sun by combining additional arguments with the insights gained from solar dynamo solutions. The polar magnetic field of the Sun is of order 10 G, whereas the toroidal magnetic field at the bottom of the convection zone has been estimated to be 100,000 G. Simple order-of-magnitude estimates show that the shear in the tachocline is not sufficient to stretch a 10 G mean radial field into a 100,000 G mean toroidal field. We argue that the polar field of the Sun must get concentrated into intermittent flux tubes before it is advected to the tachocline. We estimate the strengths and filling factors of these flux tubes. Stretching by shear in the tachocline is then expected to produce a highly intermittent magnetic configuration at the bottom of the convection zone. The meridional flow at the bottom of the convection zone should be able to carry this intermittent magnetic field equatorward, as suggested recently by Nandy and Choudhuri (2002). When a flux tube from the bottom of the convection zone rises to a region of pre-existing poloidal field at the surface, we point out that it picks up a twist in accordance with the observations of current helicities at the solar surface.