On the fine structure of magnetic fields in sunspot penumbrae

¹ Department of Physics and Astronomy and Department of Mechanical Engineering, University of Rochester, Rochester, NY14627-0171, USA e-mail: thomas@me.rochester.edu
² Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK e-mail: now@damtp.cam.ac.uk
³ Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT, UK e-mail: smt@maths.leeds.ac.uk
⁴ JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440, USA e-mail: brummell@solarz.colorado.edu

Received: 3 February 2006
Accepted: 16 March 2006

Abstract

Recent observations have revealed the interlocking-comb structure of the magnetic field in the outer penumbra of a sunspot. We have argued that this structure owes its origin in part to downward pumping of magnetic flux by vigorous granular convection in the region surrounding the spot. Here we stress the difference between the inner and outer penumbra, and correct some misleading assertions in a recent paper by Spruit & Scharmer.