Downward pumping of magnetic flux as the cause of filamentary structures in sunspot penumbrae
- 1 November 2002
- journal article
- Published by Springer Science and Business Media LLC in Nature
- Vol. 420 (6914), 390-393
- https://doi.org/10.1038/nature01174
Abstract
The structure of a sunspot is determined by the local interaction between magnetic fields and convection near the Sun's surface1, 2. The dark central umbra is surrounded by a filamentary penumbra, whose complicated fine structure has only recently been revealed by high-resolution observations3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. The penumbral magnetic field has an intricate and unexpected interlocking-comb structure and some field lines, with associated outflows of gas15, dive back down below the solar surface at the outer edge of the spot. These field lines might be expected to float quickly back to the surface because of magnetic buoyancy, but they remain submerged. Here we show that the field lines are kept submerged outside the spot by turbulent, compressible convection, which is dominated by strong, coherent, descending plumes16, 17. Moreover, this downward pumping of magnetic flux explains the origin of the interlocking-comb structure of the penumbral magnetic field, and the behaviour of other magnetic features near the sunspot.Keywords
This publication has 19 references indexed in Scilit:
- Optical Tomography of a Sunspot. III. Velocity Stratification and the Evershed EffectThe Astrophysical Journal, 2001
- On the transport of magnetic fields by solar-like stratified convectionAstronomy & Astrophysics, 2001
- Pumping of Magnetic Fields by Turbulent Penetrative ConvectionThe Astrophysical Journal, 1998
- A Dynamical Model for the Penumbral Fine Structure and the Evershed Effect in SunspotsThe Astrophysical Journal, 1998
- The Vector Magnetic Field, Evershed Flow, and Intensity in a SunspotThe Astrophysical Journal, 1997
- Magnetic structures in a dynamo simulationJournal of Fluid Mechanics, 1996
- Sun center observations of the Evershed effectThe Astrophysical Journal, 1995
- Stokes Profile Analysis and Vector Magnetic Fields. VI. Fine Scale Structure of a SunspotThe Astrophysical Journal, 1993
- On the magnetic and velocity field geometry of simple sunspotsThe Astrophysical Journal, 1993
- Dynamo action in stratified convection with overshootThe Astrophysical Journal, 1992